When it comes to MMOs... Name it and I've probably played it. I do my best to play every MMO I can, if even just a free trial, and by now my list is a bit over 200. Yeah, I have way too much time on my hands.
I played The Sims Online for five years, and played Star Wars Galaxies for the same amount (both since launch). TSO is, of course, no longer in service and I quit SWG a little while ago.
I played Auto Assault for over a year (two years if you include beta) but that is also now no longer running. Earth & Beyond was another year, City of Heroes for two years, Universal Century.net Gundam Online for almost two years, Tabula Rasa for almost a year, Pirates of the Burning Sea was around two years (including beta), Champions Online for six months... These aren't in any order.
I don't play any MMOs currently. I have yet to find anything that keeps me interested. I'm beta testing a few but I probably wont stick with them when they launch (especially LEGO Universe).
I play some free-to-play MMOs off and on... Mabinogi, Drift City, Shin Megami Tensei: Imagine Online, AirRivals, Atlantica, FreeRealms, Holic, Fiesta, Dragonica, Project of Planets, Dream of Mirror Online, Perfect World, Luna... Though I haven't played any of these for a little while...
I'm really looking forward to Star Wars: The Old Republic. Finally, an MMO that looks decent!