I am uncertain about the origin of the universe, but given the current state of evidence I would say it is equally probable that the earth began from a Big Bang without a God as that it was created by a God. I see no reason, aside from emotional gratification, for individuals to argue one side over the other. If people were being objective on the issue, then I think most people would be agnostic.
Of course, if I were to ask a Zen Buddhist, they would probably tell me that what is being debated here is perception of how the universe originated, not what actually happened, and that human conception is inherently biased to categorization and there is no way of knowing whether an understanding of the origin of the universe could even lend itself to that cognitive process. In other words the tendency to argue "either/or" on this issue when we are not even sure the ideas are mutually exclusive, is in itself, flawed reasoning.