It seems to me that you're asking if there's scientific evidence or a logical argument which proves (or strongly suggests) that there's a God.

If such a proof exists, though, I doubt it would matter. My theory is that almost all people are basically irrational (and yes, I'm including myself here). We believe what we believe or prefer what we prefer for a variety of nonrational reasons - then as a result of that premade decision, we find the "rational evidence" for one side or the other to be more credible.

So, what are the compelling reasons that so many people believe in God? I think the number one reason is the goodness in the world: beauty of nature, human love, healing, etc. Other reasons might be:
- the aesthetic appeal of religion (ceremony, music, art, storytelling)
- good things that religious people/institutions have accomplished
- social pressure from some quarters
- chance to feel morally superior to other people

Just so you don't think I'm picking on the religious here, I also think that the most compelling reasons to NOT believe in God are also nonrational... and that the number one reason is the badness in the world: cruelty of nature, human evil, disease and death, etc. Other reasons:
- bad things that religious people/institutions have done
- social pressure from other quarters
- chance to feel intellectually superior to other people

Marion

PS There's a great bit in one of Douglas Adams' books, where they create a computer called "Reason" - you tell it your dilemma, and it tells you the logical solution. But this computer was hugely unpopular, because it the solution it came up with wasn't what people already wanted to do. So they replaced it with a computer called "Rationalization": you tell it your conclusion, and it creates a syllogism proving that you're right.