Although I am a pro"ish" big bang theory and uber against creationism, I am going to play devils advocate.
The big-bang needed a seed event to have made it happen. Science can not completely explain why the big bang happened or what happened "before" it, especially seeing that we will never be able to explore into/other side of that event.
As its currently understood, there was no time before the big bang, because time needs a medium to act on (overly simplistic statement)
If there is no time before the big bang, then how could there have been a before the big bang?
If there was no before the big bang, then how could a "seed" have gone from "not big bang" to "currently banging"
The same could be said for God, Time came already pre-packaged with God. There was no God before Time, because time and God are "created" at the same time.
If infinity is possible at all, then infinitely old structures are also possible. Us feable humans are just too stupid to understand infinity.
Its like, a really big number.
(P.S. full disclosure, I know there are multiple "before big bang" theories around)