a) God wasn't created, he always existed. (to which I respond, okay, then if things can always exist, why can't the universe have always existed?)
b) God was the first thing to exist, he came from nothing. (to which I respond, why couldn't the universe come from nothing?)
or c) God created time. (to which I respond, why couldn't the big bang have created time?)
The problem is the question itself -- what was before the big bang -- it's set up to be unanswerable or to cause infinite regress.