"I am guessing every religion provides for something aspirational and exclusive in an afterlife and to varying degrees would seek to deny that to non believers."
Nothing is denied to non believers save that which they deny themselves.
"With so many religions and beliefs, can there really be a supreme being or entitiy or spirit above all others? "
Why not? Just because there are many different worldviews it doesn't follow that NONE of them could be true.
"Is it right that the Christian God or the Islamic Prophet for example would condemn billions of people who by the quirk of birth have virtually no opportunity or likelihood to become familiar with and embrace a different religion?"
No it is not right, that is also not how it works (not sure about Islam though?.
