Do Older MMOs Have The Advantage?

I don’t think I’m wrong in saying that it’s been quite a while since any new MMO has been released that’s been a major success. I don’t mean to the degree of being a WoW-killer or anything either, I just mean a recent MMO that’s done, y’know, well. RIFT’s probably the latest MMO that I can think of that’s actually proven to be commercially viable and even then I doubt it’s flaunting hundreds of thousands of subscribers. SW:TOR, The Secret World, Final Fantasy XIV, even DCU Online and Star Trek Online, all seem to just be limping by. What gives?