Where did all this matter come from? There are way more questions than answers. Earth is not a grain of sand compared to the universe.
We don't know, therefore God is a poor assumption. Must anything we don't know be the work of God?
What is this thing you call "God?" Where did it come from? How does it make a Universe appear from nothing? What was it doing before the Universe?
Exactly. Just claiming that a God did something doesn't solve any mystery of the universe. It just kicks the can down the road a little. Because the next logical question (as you already stated) simply becomes Okay, where did this God come from? What made it? How does it have these powers? Religious people can't justifiably berate scientists for their lack of being able to explain everything about the origin of the universe when the answers the religious people offer don't really explain how everything in the universe started either. God is an invented solution to the puzzle for which they have no proof.
And even if one subscribed to the "Hey all this must have come from somewhere so there must be a God" line of thinking (I don't) that generalistic notion in no way indicates which of the many gods the religions on this earth subscribe to is the correct one.
