I've gotten a bit bored of WoW lately. Flyv, my feral druid, is having a lot of fun raiding Black Temple but that's only a few hours a week. And I've done pretty much every other quest in the Outlands with him and all the PvP I care to. He's pretty well done. I spent a lot of time on a hunter alt, bringing her up to raiding as well as she can in my other guild (4/6 SSC). The imminent WotLK release has made me stop obsessing about doing all the content with her though. And I'm not about to start another alt.
So I've been seeing other games.
I've played Age of Conan off and on since the launch. Honestly? It's not that good. It's sort of amusing to play a fast melee combat oriented game for a bit. But the quests are tedious, the story isn't that interesting, and my friends tell me the endgame is basically not there. I lost interest once I got to level 20 and finished the starter zone; you're left to grind boring quests until level 30 and I just couldn't be bothered.
I played Lord of the Rings Online some when it first launched, but got bored with the gameplay and quit. (And respecced Flyv from Moonkin to Feral, thereby making WoW a whole new game.) I've recently picked it up again and really appreciate what the game is. The actual gameplay is not great; combat is laggy and slow and there's not a lot of variety, at least on a Hunter. But the art is beautiful, and of course the story is excellent. I'm playing it more like a single player RPG, enjoying the storytelling.
It's hard to imagine how any game will replace the obsessive, detailed fanaticism of the millions of Warcraft players. You don't see Conan lore nerds or LotRO theorycrafters out there, there are no rockstar endgame guilds for any game other than WoW. Warcraft is a uniquely excellent game. The actual gameplay, the button pushing and coordination, is fantastic, unparalleled in MMO development. And while I don't think the art or storytelling of Warcraft are great, they're good enough to keep people interested and having fun. And the game has its own momentum, enough people and things to do to sustain itself. That's not going to change anytime soon; WotLK will be successful. Maybe Warhammer will be serious competition, we'll just have to wait and see.
Other than WoW, the only MMO I've played that I've gotten deep into is Eve Online. That's a whole different thing, a rich and deep PvP game where the players generate their own content. That, and the economics of the game are fabulous; I played the game as a 0.0 trader hauling cargo through dangerous space to take advantage of cross-region market opportunites. Very fun, lots of "escort my slow freighter full of valuable ore through the pirates!" and "slip my fast interceptor through the hostile corporation blockade". But in the end the poor gameplay of Eve made me lose interest.
It turns out the gameplay, the actual button mashing, is an important part of a game for me. And Blizzard is uniquely good at making games with perfect gameplay.