Star Trek Online (lifetime) - not perfect, but it has a LOT of potential and Cryptic is currently giving us a ton of free content. Lifetime subs are gone now, but are rumored to come back at $300, but with no extras like before.
Guild Wars (think Magic the Gathering meets an MMO - w/ no monthly fees). Biggest issue I had with this is that the characters tend to have too many similarities (too many of the same head type, etc..). Still, a fun 'skills' based MMO (skills are like MTG cards, play off each other, etc)
D&D Online is installed, but with all the microtransactions....lets just say, things start to cost when you hit level 4....feels a bit nickel and dime-ish, plus you start out fighting rats and boring low level stuff (great !), but some of the levels have great roleplaying aspects from D&D, soooo. My least fav, but still installed
Tried Shaiya, great if you are into hard high level types of adventuring (lame single player experience, but I hear the PvP is great once you get your character's level up).
So far, STO is the best and GW ranks after it (IMO)
Tried Wow and the newbie area sucked so bad (UPS missions, so much fun !). I know it gets much better once you level up. Blizzard/Activision realizes that newbies aren't joining and is releasing some new low-level content to help attract new players. With 11+ million subscribers, they are the largest by far.
I have the LOTOR MMO, but have not tried it yet (got the collectors ed for something like $2-$3). I know they did or do still sell lifetime subs for $300 (it was $200 I heard if you knew someone who was a founder...). I hear it is pretty decent, even if your not a huge LOTOR fan (casual).
I refuse to pay a monthly fee. if there is no lifetime sub or SOME way to offset the costs (like free /w microtransactions) then you can count me out (bad enough we are paying premium price for skins and maps on PSN and XBL - remember when maps and skins were considered something to sell the core game and were offered for many months afterwards to keep sales up - now most games are dead within 6 months - weak).