But God sent some of His strongest spirits, who, with God's help, can win this battle against the evil one and help prepare the world for the Savior's Second Coming.
Note: I've collected quotes about this topic, but Scott Woodward's collection was bigger than mine, so I'm giving credit to his awesome site.
Thomas S. Monson
Although there have always been challenges in the world, many of those which you face are unique to this time. But you are some of our Heavenly Father’s strongest children, and He has saved you to come to the earth “for such a time as this” (Esther 4:14). With His help, you will have the courage to face whatever comes. Though the world may at times appear dark, you have the light of the gospel, which will be as a beacon to guide your way. (Ensign, May 2009)
In this challenging world, the youth of the Church are the very best ever. (Ensign, April 2005)
Gordon B. Hinckley
God bless you, my dear young friends. You are the best generation we have ever had. You know the gospel better. You are more faithful in your duties. You are stronger to face the temptations which come your way. (Ensign, November 2003, 82)
First, I want to tell you that I love you. I love you kids, you wonderful young people of this Church. I love you. I believe you are the best generation this Church has ever had. No generation which has gone before measures up to the stature to which you measure up. You are better educated. I think you have greater faith I think you have shown that faith and are showing that faith [more] than any other previous generation. (BYU-Idaho, Oct. 22, 2002)
Believe in yourselves as sons and daughters of God-men and women with unlimited potential to do good in the world. Believe in personal virtue. There is no substitute for it anywhere under the heavens. Believe in your power to discipline yourselves against the evils that could destroy you. Believe in one another as the greatest generation ever yet to live upon the earth. (CES Fireside for Young Adults, 9 Sept 2001)
I have every reason to regard you as the greatest generation we’ve ever had in this Church—notwithstanding all of the temptations which you face. (Church News, 4 Sept. 1999, 3)
Each time I have stood before a group of young people, there has come into my mind the great and prophetic statement made by Peter of old. Said he: "Ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light" (1 Pet. 2:9).
I know of no other statement which more aptly describes you, nor which sets before you a higher ideal by which to shape and guide your lives.... Notwithstanding all of the problems that we have, this, I believe, is the greatest generation in the history of the world. And you young people are a part of it. You are the beneficiaries of it. Its fruits are here to bless your lives if you will grasp them and live worthy of them. (Ensign, May 1992, 69-70)
Now, I'd like to say just a word to the young people here, you who are in your teens, you wonderful hope of the future, you faithful young Latter-day Saints, you who attend seminary and go to institute, you who are the best generation we have ever had in this Church: Be faithful. Be true. (Mexico City, Mexico, 9 Nov. 1997)
This is the greatest generation in the history of the world. How wonderful to be born at this time in the history of the earth. I hope you young people are grateful that this is the season of your lives…. You're not just here by chance. You are here under the design of God. (Teachings of Gordon B. Hinckley, 719-720)
Howard W. Hunter
There has been no generation in the past which has had the promise we have today in the age group between 15 and 25 years. (The Teachings of Howard W. Hunter, 117)
It is indeed a pleasure to address you [young people] this evening. It is more than a pleasure. I feel it is a distinct privilege because I realize that you are one of the most remarkable generations of youth that has ever been born.You are a people of destiny. What awaits you is almost beyond our comprehension. If you remain faithful to the Church, God will use your talents to guide his work through one of the most important periods of the world's history, leading toward the Second Coming of our Lord and Savior, Jesus Christ.Are you ready for that destiny? Are you getting ready? Do not suppose that your destiny is limited to your neighborhood, or to your city, or even to your state. Yours is a world destiny. (The Teachings of Howard W. Hunter, 121)
Ezra Taft Benson
For nearly six thousand years, God has held you in reserve to make your appearance in the final days before the Second Coming of the Lord. Every previous gospel dispensation has drifted into apostasy, but ours will not. True, there will be some individuals who will fall away; but the kingdom of God will remain intact to welcome the return of its head--even Jesus Christ. While our generation will be comparable in wickedness to the days of Noah, when the Lord cleansed the earth by flood, there is a major difference this time. It is that God has saved for the final inning some of his strongest children, who will help bear off the Kingdom triumphantly. And that is where you come in, for you are the generation that must be prepared to meet your God.
All through the ages the prophets have looked down through the corridors of time to our day. Billions of the deceased and those yet to be born have their eyes on us. Make no mistake about it--you are a marked generation. There has never been more expected of the faithful in such a short period of time as there is of us. Never before on the face of this earth have the forces of evil and the forces of good been as well organized. Now is the great day of the devil's power, with the greatest mass murderers of all time living among us. But now is also the great day of the Lord's power, with the greatest number ever of priesthood holders on the earth. And the showdown is fast approaching.
Each day the forces of evil and the forces of good pick up new recruits. Each day we personally make many decisions that show where our support will go. The final outcome is certain--the forces of righteousness will finally win. What remains to be seen is where each of us personally, now and in the future, will stand in this fight--and how tall we will stand. Will we be true to our last-days, foreordained mission? ("In His Steps," Church Educational System Devotional, Anaheim, California, 8 February 1987)
You are a royal generation. The heavenly grandstands are cheering you on. We are fast coming to the close of this game. The opposition is real and is scoring. But we have scored, we are scoring, and we will score in the future. The Lord is our coach and manager. His team will win, and we can be a valiant part of it if we so desire. Rise up, O youth of Zion! You hardly realize the great divine potential that lies within you. ("In His Steps," Church Educational System Devotional, Anaheim, California, 8 February 1987)
Young men of the Aaronic Priesthood, you have been born at this time for a sacred and glorious purpose. It is not by chance that you have been reserved to come to earth in this last dispensation of the fulness of times. Your birth at this particular time was foreordained in the eternities. You are to be the royal army of the Lord in the last days. You are “youth of the noble birthright.” (Hymns, 255) In the spiritual battles you are waging, I see you as today’s sons of Helaman…. Live up to your godly potential. Remember who you are and the priesthood that you bear. Be modern-day sons of Helaman. Put on the whole armor of God. (Ensign, May 1986, 43-45)
Never has the Church had a more choice group of young people than at present, and Satan is well aware of who they are. He is doing everything in his power to thwart them in their destiny. He knows that they have been sent to earth in this crucial period of the world's history to build the kingdom of God and establish Zion in preparation for the second coming of the Lord Jesus Christ. Yes, our youth have an awesome challenge. ("Challenges for Leaders of Aaronic Priesthood," Salt Lake City, Utah, 19 September 1979)
Our young people are not just ordinary people. They are not just run-of-the-mill. They are choice spirits. (The Teachings of Ezra Taft Benson, 554)
Our young generation, as a group, is even more faithful than the older generation. God has reserved you for the eleventh hour—the great and dreadful day of the Lord. It will be your responsibility not only to help bear off the kingdom of God triumphantly but to save your own soul and strive to save those of your family. ("Fourteen Fundamentals in Following the Prophet," in 1980 Devotional Speeches of the Year [Provo, Utah: BYU, 1981], 26)
You have been born at this time for a sacred and glorious purpose. It is not by chance that you have been reserved to come to earth in this last dispensation of the fulness of times. Your birth at this particular time was foreordained in the eternities. You are to be the royal army of the Lord in the last days. You are "youth of the noble birthright". (Ensign, May 1986, 43)
I am sure that I am looking into the faces of one of the choicest groups of young people that have ever come to this earth. It is my conviction that in this dispensation some of the choicest spirits of all time are being sent to earth to help bear off the kingdom, to help provide leadership in a time of great need....You are a youth of a noble birthright, but your progenitors cannot save you. Each one of us must work out our salvation individually by making personal choices. We are each personally responsible. (May 24, 1961, BYU Speeches of the Year, 1961, p.3)
It is my conviction that the finest group of young people that this world has ever known anything about has been born under the covenant into the homes of Latter-day Saint parents. I have a feeling that in many cases at least, these choice spirits have been held back to come forth in this day and age when the gospel is upon the earth in its fulness, and that they have great responsibilities in establishing the kingdom. (CR April 1951)
Harold B. Lee
You, our youth of today, are among the most illustrious spirits to be born into mortality in any age of the world. (The Teachings of Harold B. Lee, 627)
I remembered something that my wife handed to me from an address given by George Q. Cannon some time ago in which he said some very interesting things which I fully believe. These are a few of his words:
And there is this to be taken into consideration, God having predicted the ushering in of the last dispensation, knowing the odds that would have to be contended with in establishing it: God knowing this has reserved in the heavens to come forth at this time the noblest of His spirits, the men and women most capable of carrying out this work, and achieving the grand results the Prophets have predicted should be accomplished in the day and generation, preparatory to the coming of the Son of Man. God knowing this, in His wisdom and foreknowledge has prepared the way beforehand, and there will be men and women brought forth who will carry off this work in the way He designs. (Journal of Discourses, 25:26.)
You are among those of whom he was speaking. This is your day and your time. You have been brought forth in the most auspicious time in the history of the world, to help in bringing to pass the preparing of the people to be ready to receive the coming of the Lord. (The Teachings of Harold B. Lee, 626)
The Lord has chosen a small number of choice spirits of sons and daughters out of all the creations of God, who are to inherit this earth; and this company of choice spirits have been kept in the spirit world for six thousand years to come forth in the last days to stand in the flesh in this last dispensation of the fulness of times, to organize the kingdom of God upon the earth, to build it up and to defend it and to receive the eternal and everlasting priesthood [of God]. ("Our Lineage," Topical Outline to the Way to Perfection, (Salt Lake City: Genealogical Society of Utah, 1932), p. 4)
George Q. Cannon
God has reserved spirits for this dispensation who have the courage and determination to face the world, and all the powers of the evil one, visible and invisible, to proclaim the Gospel, and maintain the truth, and establish and build up the Zion of our God, fearless of all consequences. He has sent these spirits in this generation to lay the foundation of Zion never more to be overthrown, and to raise up a seed that will be righteous, and that will honor God, and honor him supremely, and be obedient to him under all circumstances. (Journal of Discourses, 11:230)
And there is this to be taken into consideration, God having predicted the ushering in of the last dispensation, knowing the odds that would have to be contended with in establishing it: God knowing this has reserved in the heavens to come forth at this time the noblest of His spirits, the men and women most capable of carrying out this work, and achieving the grand results the Prophets have predicted should be accomplished in the day and generation, preparatory to the coming of the Son of Man. God knowing this, in His wisdom and foreknowledge has prepared the way beforehand, and there will be men and women brought forth who will carry off this work in the way He designs. (Journal of Discourses 25:26)
Boyd K. Packer
We notice, as we travel about the Church, that our young people are stronger than heretofore....
You are better than we were. I have the conviction that against what was surely coming and the prophecies that were given, the Lord has reserved special spirits to bring forth at this time to see that His Church and kingdom are protected and moved forward in the world. ("Lehi's Dream and You," BYU Devotional, 16 January 2007)
Russell M. Nelson
If my fondest wish could be granted, it would be that we could know who we really are, and that we know we come from premortal realms where we were numbered "among the noble and great ones who were chosen in the beginning to be rulers in the Church of God.
"Even before [we] were born, [we], with many others, received [our] first lessons in the world of spirits and were prepared to come forth in the due time of the Lord to labor in his vineyard for the salvation of the souls of men" (D&C 138:55-56).
Our precious identity deserves our precious integrity! We must guard it as the priceless prize it is. (Perfection Pending, 29-30)
You are one of God's noble and great spirits, held in reserve to come to earth at this time (see D&C 86:8-11). In your premortal life you were appointed to help prepare the world for the great gathering of souls that will precede the Lord's second coming. You are one of a covenant people. You are an heir to the promise that all the earth will be blessed by the seed of Abraham and that God's covenant with Abraham will be fulfilled through his lineage in these latter days (see 1 Ne. 15:18; 3 Ne. 20:25). (Perfection Pending, 79)
Every man who has received the Melchizedek Priesthood has been foreordained from the foundations of the world for that privilege. Every Latter-day Saint woman has been foredetermined to come at this time to participate in partnership in building up the Church and kingdom of God upon the earth as part of the preparation for the second coming of the Lord (Perfection Pending, 206.)
Click here for a more recent talk about Becoming True Millenials by President Nelson.
L. Tom Perry
You are a chosen generation—saved for this special time in the history of mankind. You have so much to give to add to the growth and development of the families to which you belong. I challenge you to step forward in your family units with that special, enthusiastic spirit of your youth to make the gospel really live in your homes. (Ensign, May 1994, 38).
Marvin J. Ashton
I thank God continually for the young men and young women of this generation. I firmly believe that the finest young people that have ever lived in the history of the entire Church are with us today. (Ensign, November 1989, 36)
Click here on more about being a chosen generation.