Not an atheist, never have been, but when I have doubts I look to the beginning. You have 2 choices. Either everything came into existence out of nothing on it’s own (impossible), or it was created (which is the only logical answer).
Now we have another choice would this God reveal himself or just not bother anymore (deism). I believe if a God took the time to make it he would be interested in it and reveal himself to humanity in some way.
so now we have another choice Monotheism or polytheism. I think if a God would be interested and revealed himself he would still be worshipped. Since polytheism is largely dead and the vast majority of humans worship the same God, the God of Abraham, then he must be the real God.
So we have Islam, Judaism, and Christianity. Well Christianity is the only one that says we are all equal in Gods eyes, not to mention its very well documented how these people( the apostles) ran for fear when Jesus was Crucified only to go to their death claiming he has arisen.
So then we have Catholicism, protestantism and Orthodox christianity. Well history shows that The Catholic church is the original church. Enough said.