True enough, but my point was rather that 'God' can be defined in many ways, including 'the force that created the universe'...which doesn't actually differ that much with a Big Bang Theory. You could increase the definition by saying 'the force that created the universe in a guided way', and it would still not differ that much.
Theists also differ among themselves on who & what God is, and often go so far as to say he can't be understood (in which case, my question would be - how do they define something they can't understand)
Then you have your agnostics, who believe in God, but not the religious version.
Who's correct, and which one are you going to going to choose when you say "I don't believe" or "I believe"?
Hence why I think you would need to define 'God' first.