Atheists who have read the Bible (or parts of it, like me) often say that God's actions are inconsistent (especially when reading the Christian Bible) but what strikes me the most is that whatever theologians say about the folly of anthropomorphizing God, he is a very human figure as portrayed in the Bible. This is especially true if you don't buy that the inconsistencies in his actions are due to greater knowledge. If you treat him as a petty and sometimes foolish character, it makes sense. But this is not an interpretation that works well in a monotheistic framework, at any rate not a conventional one.
However, there is some evidence that early Jews believed in more than one god, and that many didn't even confine their worship to their own tribal god (the god of the Bible). Modern Judaism, of course, doesn't support this view, but I am rather fond of it - I like the drama of a group of quarreling deities, as in the Greek and Roman myths, rather than the comparatively boring idea of a single benevolent creator, or the frightening one of a single strict or even vindictive deity.
But the reason I think that God has to be human (by which I mean that as a character he is humanlike) is that we only know one intelligent species capable of communication - Homo Sapiens. It would be difficult, if not impossible, to imagine an intelligent being that was not humanlike (which is also part of why most science fiction aliens look a lot like us). He has to either be a humanlike character or a non-character.