World of Warcraft takes place in Azeroth. Age of Conan's setting is Hyborea. Guild Wars boasts Tyria as its location. Lord of the Rings Online has Middle-Earth, which Tolkien refers to as much as an age as a location, hinting that it could in fact be Earth's past, but the landscape as described doesn't really match anything in our reality.
And what does Earth have? Hellgate: London, The Agency, The Day, and possibly The Secret World. While there may be supernatural elements in a couple of these titles, for the most part they belong firmly in a science-grounded reality, and couldn't be considered true Fantasy settings. So what gives? With the unlimited imagination on display for all these other titles, why does Earth get short shrift? Is there any good reason for our fair Terra to be left out of the Fantasy loop?