SWG without a doubt.

DAoC is the only game that made me get up at 4 in the morning just to get some gaming hours in before school.

So DAoC without a doubt. The atmosphere in the start zone when I started out as a Highlander was pure magic.

1) DAoC (Even after Trials of Atlantis)

2) EvE Online

3) SWG

All Sandbox, even DAoC.  I don't care what raid garbage they tried to cram into it later, all the good stuff was PvP Sandbox Keep Sieges.  All had solid crafting that actually mattered.  None really had much in the way of the WoW quest structure (which I despise).

I don't want to use the word "best," but by far my favorite was SWG. 

That game pretty much destroyed MMOs for me going forward.  Every game I try is compared to SWG, fairly or not.  SWG was the most immersive, detailed, open, entertaining experience behind the monitor I have ever had and probably ever will.  The game had it's problems, I do not deny, thus, I cannot call it the "best" (probably give that to EvE.)  But no other game have I so willingly given so much of my free time.

I've been playing WoW on and off for 8 years... and right now I'm back "on" and am having a great time playing in a new way.

Though I have very fond memories of my earlier MMO experiences (UO, E&B, SWG) nothing since 2004 has really had that same hook and I just can't argue with 8+ years of great (at times) game play.

My list is:

Short-term: DAoC pre-SI. That was the most fun I had ever had in an MMO but it didn't last unfortunately. I hated the addition of the superbuggy Animists in RvR, which is what I primarily played for. After SI, the game started a slow decline.

Medium-term: EQ2. I hate the engine though and prefer the game when it was a bit harder.

Long-term: WoW and EVE. EVE is the game I played  the longest, but I played so much of it that I got tired of it. I have not been back for several years and don't feel that strongly inclined to go back.

WoW is the game I have played the second longest and I am still enjoying it with no plans to leave even though I was disappointed initially with MoP.

Honorable mentions: GW1/2 and AO.

If I were recommending games to someone just coming into the MMORPG genre, I would recommend WoW or EVE. I still think those two games are the top of what the industry has to offer for themeparks and sandboxes.

1st/2nd: swtor and wow, not sure which too put first

3rd/4rd: rift and gw2, again not sure which to put 3rd

Best as in 'Quality' overall? Guild Wars 2.  Not a single bug encountered thus far, amazingly.

Best as in the one I had the most fun with? Star Wars Galaxies... but obviously, that was not a bug free game hehe

Hands down the best I've ever played was UO. The game is well over a decade old and still going with a monthly fee I might add lol. It's that one game I come back to from time to time. I just recently went back for another 3 month stint. 

Player Housing - Customizable player housing, with millions of items to decorate it with from the practical to the purely cosmetic. It's real time housing as well, not some instanced crap no one can see but those you invite. 

Be what you want - The only game that lets you be exactly what you want. The skill system has yet to have an equal. Pick the skills you want to, play how you want. Want to be a mage with a crossbow that happens to have a pet dragon? Go for it. Want to be a Gargoyle warrior miner? Go for it. 

PvP and PvE - It's not an action based combat system, it doesn't have the best or even decent graphics, yet it offers some of the best PvE and PvP out there. Full Loot FFA PvP if you go to feluca and Solo, Group, Small Group, Guild PvE content in abundance everywhere. Players have even made there own events in both PvE and PvP. 

Simply put no game has been able to offer what UO does. They don't offer the freedom, the ammount of content, nor the ammount of customization. 

This is why I always go back lol... games dated as hell in graphics and such, but the mechanics and such are well beyond any current game. 

Best MMo I played was Star Wars Galaxies. The player driven economy with player citys and housing thrown in with open world planets with pvp and pve. And the elusive Jedi grind ( man do I miss that ).

However, the MMo I played the longest was World of Warcraft. It is the best MMo out there right now. People can hate all they want, but I have played nearly every big titled MMo on the roster and non of them compare even in the slightest.

Here is my list from 1st mmo to last. Ive played up to 3 MMo's at one time.

SWG ( quit at nge, but went back a few months before they shut the lights out )

City Of Heroes ( got to level 32 and quit )

World of Warcraft  ( Played off and on for 8 years or so, longest I left for was a year )

Dungeons and Dragons Online ( got to level 8 and quit )

Lord of The Rings Online ( got to level 20ish and quit )

Everquest 2 ( level 18 or so and quit )

Aion ( have 3 level 55 characters, played for about 2 years, havnt logged on in about a year )

Star Wars The Old Republic ( have 2 level 50 characters, havnt played in months )

The Secret World ( end game on one character, havnt played in months )

Guild Wars 2 ( level 64 Ranger , havnt played in a few months )

At the moment I am two boxing on WoW with Recruit a Friend perks and having a blast.

Might try Wildstar and Skyrim when they release, but I am staying with WoW for now. its the only game worth paying for.

Best overall feature set: GW2

Best lore and world: AoC

Most PvP fun: STO in early days.

Most interesting mechanically: EVE, GW1

Best for teamwork: Pirates of the Burning Sea