If there was a God who existed and was prepared to punish you for not believing in him, then if this God was fair, it seems that there would have to be some pretty good (obvious) reason why he could expect everyone to believe in him. Even if some of these difficult (for me) cosmological or ontological arguments are any good, then a fair God could hardly punish you for making an incorrect evaluation of such difficult arguments. So maybe there is another reason why God could expect someone to believe in him - could you maybe make a decent argument as to why someone should believe in God along these lines:
It seems (obviously this is controversial) that there is something a bit more virtuous about believing in God than in not. What I mean by this is that belief in God seems very humbling, optimistic, honest and hopeful, whereas rejecting the existence of God seems a bit more cynical, easy and self-centered. In other words it is a better reflection on a person's character if they believe in God than if they don't. If we should act virtuously, then, it looks we should believe in God, because doing this would be acting virtuously.
Even if this argument is any good, though, it doesn't seem to show that God exists, only that someone should believe in him. But if it is true that people should believe in God, then wouldn't it be very remarkable that this would be the case if there was in fact no God?