There are at least six religions built on the foundation of Genesis. All six read slightly different things into the narrative. So there's that aspect. Most Christians and Jews do not believe that Genesis is more than historical allegory. It's just not needed when you get right down to it.
But you're also misunderstanding what it means to believe and why you should do it. Religious belief is supposed to be a fun, interesting, mysterious thing to do, not an ugly, boring thing that you do because you have to. Most Christians have lost sight of this in their incessant quest to "save souls."
If you don't like Christianity, I'd say you don't really understand it yet. Christians understand just how irrational their beliefs are, yet do it anyway. Jesus is just that great of a thing to believe in.
But this is your culture and your heritage. You're not obligated to believe in it, but I do think you're obligated to make peace with it. Living out of sync with your brethren isn't really all that it's cracked up to be.