Often, when I bring this up, I am told that I prefer fantasy over reality, that I have a "whats in it for me" approach to a relationship with God, and that I dont look at what other religions and human literature have to say on the subject.
I don't think a purely selfish motivation is at play.
My own experience is that there is a difference in worldview. I can't speak for all atheists, but one of the major observations I have made is that atheists can make peace with the idea that the universe could care less about our existence. Ultimate, atheists are interested in what IS true, not what they HOPE is true.
Theists, on the other hand, seem to have a need that something out there does care about them. I would call that a very human reaction, not really a selfish one. In the end, I would define the essence of faith and belief as hope. The interesting bits come when that hope butts heads with facts.