This is excellently put. It is indeed the starting-point issue, I think. When we are considering the belief in a Supreme Being, are we merely listing the delusions of the primitive that have no reference to reality, or are we discussing a profound human attraction to the Source and meaning of our existence.All this leaves us with the question, did early humans realize these concepts from within and create the concept of God, or is there a supreme being that put these concepts into the very make up of humans when the animal was raised up to be human?
Interestingly, the Bible actually acknowledges the problem. It says, "He who comes to God must believe that He is, and that He is the rewarder of those who seek Him." In other words, they can't get anywhere unless they are at least prepared to entertain the hypothesis that God does indeed exist, and that He wants to be found. Apart from that, we are inevitably back to the situation above: that is, we have two alternate ways of trying to account for the "religious impulse," and no way of ever finding out which is right.
The game-changer is the second part of the question: it is of primary importance that the Supreme Being "is," of course -- but that fact in itself is useless if He does not want to be found. Then we would still be stuck, with no one knowing any more than anyone else.
In short, the main question is, "Has God spoken." If not, we probably ought to forget the whole question: we're all just fools playing a guessing game, and we have practically no chance of figuring the answer out. But if the Supreme Being should ever have decided to reveal Himself to us, we might have a crack at getting somewhere.
That, I think, is why all "religions" suppose that there is some communication available from "the other side," so to speak. So all religious persons see the problem differently than the religious skeptic. They look for evidence of genuine Divine communication, whereas the skeptic naturally seeks to "explain away" what he is looking at. For the skeptic, the only question is, "How do I explain and dismiss this bizarre phenomenon known as religion?"
Attitude matters. In fact, it's determinative.