When I am thinking according to my true nature of pessimism, this is my opinion about Heaven, Hell and God:
Somebody once upon a time was pretty greedy and wanted a way to control the stupid masses, so (they) invented God and Hell firstly to scare people (what better scare tactic than the fear of eternal damnation). They then introducuced Heaven and Salvation as your hope for escaping damnation.
Of course, there was a list of what you could be sent to Hell for, murder, theft, adultery, self-righteousness, etc., and most important of all, not believing in God.
Once people began to accept Hell, as the years went on, and were in fear of being bad in any way, they then could accept salvation. Religion then gained foothold financially, materially and grew in power, as those controlling the religion dictated to the people what God's will was, until now religion is truly one of the greatest defining forces in the world.
If you step back from religion, people for the most part could live happily without it. In general people are good, and the world over each religion basically holds the same moral beliefs, murder is a crime in every nation, theft is a crime, adultery is frowned upon or forbidden, and etc. Each religion gives its own lesser rules to the society, and some religions are forced to renounce or revoke some beliefs if society at large does not accept them (mormons and polygamy..).
At different times in history religions have held very great power. The Catholics and Christians held a lot of power in the past, the Muslims as well, the Jews, Communists. And different areas of the world have their own religion which has held stronger and lesser power over the centuries.
My point is, I sometimes feel that religion was one of the greatest scams pulled on civilization, and that while it has its place, maybe mankind will eventually be able to live in peace without it.
Never has the world had peace with or without religion. Perhaps it is in man's heart to control others, to gain power, to be the one with 'the answer', and at the point in time when each person can accept another person as they are, religion or no religion, without feeling a compelling need to "save" someone who doesn't believe the way they do, then we will have true acceptance of one another.