The world is exactly what you would expect if there were no God, and pretty much the opposite of what you would expect if there were a God. The only way this world makes sense if there is a God is if it is all a big "Test" to see if we will keep believing in God when the evidence is to the contrary. And this is just the Theist way of saying that the world seems godless to them, too.

What's compelling varies by person. And what initially compels a person to change their beliefs isn't necessarily the strongest possible argument. It is what reaches / touches them where they are. In my case for example it was the repeated and spectacular failure of religious dogma to accurately predict or explain my lived experience. But later I understood that it was fundamentally an epistemological problem -- an inability to ground religious precepts in reality and established truth. For the most part religion asserts facts rather than establishes them. To me that is the fundamental issue. But that understanding came later, after the emotional impact of various disillusionments and disappointments.

As Fernapple says, which god?

You will need to be more specific as many cultures embrace the idea of an overarching spirit which has more validity than an anthropomorphic god.

The most compelling argument against the existence of a literal god, for my money, is the mountain of evidence that illuminates our psychological (as well as biological) need to create gods. There is no proof that gods don't exist, but there's a ton of evidence that explains quite clearly why we invent them.

Just. Which God?

When there are ten thousand or more known gods, and even more sects claiming to be the only true version, the chances that any one person has hit just by luck on the only perfect choice, makes the national lottery look good. So that if they raise the question. "What if you are wrong ?" Then you can say, with perfect logic. "Well if I am wrong and there is a god, then we are almost certainly both wrong."

I'll keep it simple, there is no god