Desiring greatness is not a sin. I think on some level, all of us desire to be great; to have power, presence, and influence that can be used for the Lord. Whether you want to be a great mom, a great soccer player, a great teacher, a great architect or a great musician, I don't believe these desires are wrong in and of themselves, but I believe they can become wrong when the desire to be great supplants the desire to be godly.
As a young pastor, I have a lot of men who I very much look up to. Every morning I go running and during my runs I listen to some of the world's best preachers: John Piper, Mark Driscoll, Francis Chan, James MacDonald, Matt Chandler and the like. I pick apart every aspect of their sermons: their speech, their cadence, their word choices, their pauses, their illustrations and their passion. I think, "Wow! These guys are incredible! They really know their stuff, they are passionate about God, they are great communicators of His truth, and they are effecting large numbers of people for the kingdom! I want to be like them!" In the bottom of my heart, I want to have a ministry like theirs and to be as effective as they are. But that's the problem...I want to be like them. My desire is to be like these great men...when in reality, the only reason these men are great, is because they are godly! The only reason these men are effective is because they earnestly desire to know and love the Lord. That is why God blesses them and entrusts them with awesome ministries; that is why they are able to speak boldly without the fear of man, that is why they have such effective ministries. They are great only because they are godly.
God has been really challenging me with this lately. I should not desire to be a great pastor...I should desire to be a great God-lover. I should not desire anything else but to know God, love God, and please God. If I desire anything else above that, I will sabotage all that God intends for me to be. He should be my greatest and highest longing. Love Him more than anything else, desire Him more than anything else. Truly, there is nothing greater than loving God and being in the center of His will; it is in this that we become great. True greatness comes only from godliness!
Seek first the kingdom of God....