The concept of God is incompatible with my scientifically derived views of the world. I believe in indeterminism, and thus omniscience is impossible. I don't believe that there are ultimate things such as utopia, ultimate goodness, ultimate evil, etc, and this is incompatible with an ultimate creator and the qualities of the monotheistic gods. The concept of God is logically inconsistent. How can there be evil in the world if God is good.
Outrageous claims require outrageous proof.
If you told me you had pizza for lunch, I have no reason not to believe you, and I would accept your claim unconditionally. This last recuirement is, of course, not appliable to miracles, but there are many other ways of proving something than scientific reproducibility. The bible is not like it would be if an omnipotent, omniscient, good god, who wanted us to believe in him, had written it. Thus the Christian god is unsupported by the christian scripture. I find it impossible to know which, if any, of these religions is the right one.