Many religious faiths, including the big three Abrahamic faiths, teach that humans are central to the universe and God’s Plan. It is indoctrinated in us from childhood, so much so that it becomes a mantra: we are special; we are unique; we are created in God’s image; the universe exists solely for us. How can naturalism, with no guarantee of eternal life and no preferred position at the right hand of God, possibly compete with its ego-massaging and death-defying religious counterparts?
I believe the answer lies, at least in part, in a sadly unexplored arena: the ability of atheism (scientific naturalism) to be spiritually uplifting. Not "spiritual" in the sense of a religious spirit or soul, but rather in our innate ability to be awed or inspired. I can't speak for the religious, but I cannot imagine anyone feeling a greater sense of the spiritual than I do when I look up at a starry sky on a cloudless night. I've said it before and I'll continue saying it: There is more awe and wonder in one chapter of an introductory astronomy book than in any ten Bibles. No one, though, as far as I am aware, has ever adequately demonstrated in the mainstream that it is possible to live a spiritual, meaningful existence without a belief in God.