[Veritas]

I don't think that you could say that Middle-Earth is a religion. Not in the way of the Bible, the Koran and others. It doesn't exist that long, and people now know much about how the Earth is made and the stars. People have less need for a religion to believe in. Don't get me wrong, I say Less, not No.
As Beleglas said, if it was writen earlier, then there would be a big change that it would be a religion, but it's not. It's something where you can dream over in your fantasy. But believing that it would really exist? No, I don't.