World of Warcraft is the only MMO I've ever played, so that, really. During my time playing it I had no desire to try out anything else, aside from a brief period when I lost a bit of faith after Wrath of the Lich King launched (but I still stayed with the game for a further two expansions, so it didn't last :P)
I've played Phantasy Star Online but I'm not entirely sure it was an "MMO" RPG. I've also played MAG which apparently is listed as an MMOFPS on Wikipedia, but again I would consider it lacking the "MMO" aspect.
Kind of off topic, but in future I'm planning on trying Final Fantasy XIV (when it comes to PS3); and Planetside 2 either if it comes to PS4, or when I decide to upgrade my computer.







