Are atheists and humanists morally superior?

I agree with your logic but I wouldn't say we are superior in any way. Everyone is still looking out for their personal interests. There are some religious people that are as concerned with this life as the "afterlife". If we were concerned with social fairness, quality of life, and suffering without thinking about personal interests ("this life is probably it") then you could say Atheists and humanists are morally "superior". I hope that makes sense.