Surely Jesus understands nuance and will give an all clear heaven's pass to someone who is an atheist but still an essentially good guy? Or is he mean and dictatorial and say 'thou shall worship me else you will rot in hell' ?
The Bible (at least as far as the New Testament is concerned) is absolutely and explicitly clear on the matter. Being an "essentially good guy" doesn't matter, nor does being an amoral bastard - if you sincerely accept Christ you go to heaven, otherwise you burn in hell.