Believing in God is without a doubt the most centric part of practicing most of today's great religions. The idea is that God tells us about his existence through different methods (nowadays through the Bible and people who believe in him), and that we get to choose whether we want to follow him or not. This obviously leaves a lot of room for interpretations: Some think that following God's message (i.e. being a good person to your fellow human beings) is the most important part, others put close- or even equal value into believing that God himself actually does exist, or even that believing that he does exist is a must if you want to enter his kingdom after you have died; given that you have been informed about the concept of God, of course.
That is where I see a problem. Why would God care about whether you believe in him or not? Saying that God would care about whether you believe in him is even more absurd considering that you don't actually choose what to believe in. For example: I believe that the world will not end on December 21st. Why do I believe that? Because there is no evidence supporting that the world will actually end on that date. I don't choose to believe that the world won't end in December, the circumstances makes me not believe it: My personality makes me demand evidence, or at least theories supporting my beliefs and disbeliefs.
In another example you will ask a kid if it believes in ghosts. The kid's answer is, "Yes, I have seen many ghosts at night so I have every reason to believe in them." This could obviously be applied to some adults as well, and what they would have in common are their personalities which does not require empirical evidence for them to believe that what they think they saw actually exist.
The bottom line is that your guts decides your beliefs, not your will. For example, I can't suddenly choose to believe in fairies and elves, some pretty damn major events would be required for me to change my stance on that one. Of course, you could change your guts' stance by doing some research or having some sort of revelation through meditation or something like that, but in the end your guts will always be the 'boss' of your beliefs. It is possible to ignore your guts and say, "Obama can't possibly have been born in America!" despite knowing very well that your belief is completely unsupported, but that would put you in denial.
So, with that said, why would God put any value into what we believe in? I mean, if a person has tried his entire life to educate himself about, for instance, the Jewish faith, all because he wanted to share the same belief that all his relatives had, why would God be disappointed if his guts still told him that God does not exist, resulting in him being an atheist? How could a god, which claims to be fair and just, possibly demand that you ignore your guts and live your entire life in denial?
That, my dear friends, makes no sense.