I've been playing
EVE-Online for three and a half years now and it's still very enjoyable (and will continue to be). It's an mmorpg situated in space where you fly around in your ship (frigate, interceptor, battleship, etc.) and either do missions or fight against other players.
If you like fiddling around on the market you'll find EVE's ingame market very interesting as prices etc. are decided by the players (except for skillbooks you buy from NPCs). If there's a war raging between player alliances (which it is all the time), demand for ships etc. will go up and the market will adjust accordingly. Kinda interesting.
The PVP is as real as you can get it. It's nothing like WoW's wannabe "pvp" where you don't lose your stuff when you die. By attacking another person in EVE you risk your ship and everything you've fitted on it, but if you win you can loot his wreck and get some valuable items.
EVE is the biggest mmorpg in the world in terms of players on one server. I think there's about 200 000 characters in the game now and there's usually always around 30 000 logged into the server at once. So there's no divided servers or any shit like that which WoW uses. They have one more server though, but it's for China only (due to their weird laws I think).
Also worth to say that a lot of people who used to play Planetarion find EVE enjoyable.