Don't take this the wrong way, it is just my personal opinion....
Which religion would win?... NONE. No religion would win over another because Man was never meant to have religion in the first place. When God supposedly created Adam and Eve in the Garden of Eden, did he give them both a copy of the Bible and say unto them "you must be Christians and follow the bible or else"? I don't think so. When humans first evolved on the planet (if going the evolutionary route) did they carry around bibles? Did they have religion? I don't think so. They lived amongst the animals and lived like the animals. No religion, no God. That's the way things should be in my opinion. That's the way things were in the beginning. If there were a God, would he not have just preferred humans to stay the way he originally created them? Pure, natural, and simple? Did God intend for there to be religion? I don't think so. I think humans have gone too far already. We must step down from our "minds" and our "egos" and learn what it's like to be animals once again. Animals are closer God. After all, animals never got kicked out of the metaphorical "Garden of Eden" did they? Yet they still live amongst us, why is that? In my opinion, humans are simply animals that have lost their way.