I believe in a God, because I don't believe something came from nothing. You can't say the big bang is real, for something had to cause it. But, to just look at earth, and say we came here from just a (Load of theories, place here), is complete nonsense.
So really, comes down to if something was always within the universe. Some sort of gas (Anything really) maybe, but you can't believe gas was always within the universe, and had no beginning. But, to believe in someone, to create something as magnificent as the universe, and had no beginning. Seems more logical.