By that last definition, both humanism and atheism could be considered religions, and I know several atheists who are as annoying as evangalists when it comes to trying to convince other people to believe as they do...

UFOs being a new religion? Definitely. There are cultish groups out there that make yearly pilgrimages to Roswell with a devotion that inspires comparison to Islamic pilgrimages to Mecca. They have an almost desperate need to believe that there is something greater than the sum of humanity out there, and they've found it in advanced alien cultures from other worlds.