#1 UO. Till Renaissance expansion. Quite simply the greatest MMO ever. It was created as a blank canvas with a myriad pallete for the players to create their own world. Nothing else has come close.
#2 DAoC. Till ToA....it's the game WoW cloned and, despite absolutely frustrating devs (anybody else remember them denying berzerkers were overpowered for a year and a half?), it was the most complete MMO (PvP with a purpose -- albeit a contrived and frivolous pupose -- and solid PvE ripped from EQ).
#3 UO. Post Renaissance expansion. Game is now totally different but offers a LOT to do and experience...BoDs, artifacts, custom housing, factions, runic crafting tools, flower growing, etc.
#4 Shadowbane. For the first few months before the bugs in the end game were all uncovered. Underrated graphics were spectacular...only game with realistic designs. PvE was more fun than it should have been. Poor coding and balance doomed it. First game you could actually fly in.
#5 City Of Heroes. Shallow gameplay, but quite entertaining with all the varied power set combinations and costumes. Kind to casual players.
#6 WoW. It's just like DAoC but shinier and has orcses!!! If you never played another MMO this would blow your mind, but having played some EQ and DAoC, this felt like playing the same thing.
#7 AO. Innovator of the instanced mission and very cool futuristic style. Quite convoluted and uninspired past that. Best sound track of any MMO save the brilliant MIDIs from early UO.....seriously the Vesper town music from UO will almost make you weep.
I also played some EQ but I thought the game sucked so bad I won't even rate it. Entirely group-centered level grinding. I, unfortunately, never played AC but it sounds like a good one. I beta tested SWG, but didn't play post release....on paper was the ideal MMO, but as a seasoned MMO vet by the time it came out, I couldn't stop looking past all the glitz and seeing the same old gameplay, plus it seemed like it was geared for the player with lots of time to invest and I was married by this point. Beta'd E&B, but it needed deeper gameplay to make up for the boredom of flying through space so much.
I'd love to go into more depth, but I'm typing this with one hand while cradling my two week old in my other arm.
Oh, and anybody who played Albion is a pansy.