i can't believe in a god who says i must believe in him before anything else matters, but to be fair, no god ever asked me to do so. really it was his interpreters.
good and evil isn't merely a matter of perspective. saving lives thru science or other 'good' deeds is good. being cruel or stealing from the poor is bad. wanting to be more altruistic is good. hunting hamsters for sport is bad. seeing good vs. evil as us vs. them, yes, there can be a lot of perspectival bias there.
i don't recall any existence before i was conceived and don't expect any after i'm gone. is that a license to do as we each please? well, society at least sometimes pays lip service to the ideas of crime and punishment. i hold out hope that advanced alien races will be fairly respectable sorts.