Going to have to agree with remmus and DeadlyFred here: too much sameness, not enough difference. Just about everything being released is a fnatasy-based game, following the "WoW-formula.
The problem is you can't do that. WoW now has a 5 year jump. If / when a "WoW-killer" appears (and it will), I suspect it will be outside of what we expect from an MMO. It will have to be, to get people to give up WoW or add a second subscription. TOR is looking like it might have potential, with a heavy moral tone to it (quests that change your individual story line, depending on your decision). Will it? No way to tell - too many games have been hyped as the next EQ/WoW since they were released. AC1&2, DAoC, AO, SWG, Conan, WAR and more - all hyped, but failed in the end.
So, overall, no, MMOs aren't overrated. If anything I think some are underrated as they got lost in the shuffle.