It's tough for me to come up with a top 5 because I've really only thoroughly enjoyed one MMORPG and it was Asheron's Call.  However, I have played a lot of MMO's so if I had to place them in a top 5 list...

1. Asheron's Call

2. Ultima Online

3. World of Warcraft

4. Dark Ages of Camelot

5. Vanguard

1. Earth & Beyond

2. Eve

3. SWG pre/cu

4. WOW upto BC

5. Tabula Rasa

1. Vanilla WOW

2. GW1

3. That's about it.  

#1. SWG (First year)

#2. EverQuest II

#3-5. just as bad as every other post-wow turd.

1. WoW

2+ All turds! (That was for you mmoDAD !! ) 

1a. WoW

1b. Age of Wushu 

2. EVE

1.  EverQuest

2.  Dark Age of Camelot (before ToA)

3.  Star Wars: Galaxies (pre CU)

4.  Asheron's Call

5.  World of WarCraft (Vanilla)

1. DAoC

2. SWG

3. CoH

4. WAR

5. PS

Not in any particular order

1) Rift; Currently my main MMO.  I can't find any other MMO that draws me in like this one.

2) World Of Warcraft: Vanilla-Wrath; My most played MMO.  Played on and off until Pandaria came out, Got a monk to 90 and quit before I was even able to join LFR

3) Maple Story; May seem silly but I played the hell out of this game until I started getting into more graphic demanding games.

4) Wurm Online; When It first came out I was in awe.  It was my first true sandbox MMO.

5)Eve Online;  I have never gotten deep into the game but it is one of those games that I admire and respect.  I would love to actually be good at the game.

top 5:

1. gw1
2. aion
3. gw2
4. tera
5. aoc

1. AC1

2. UO

3. DAoC

4. Shadowbane

5. EQ1

1. Ultima Online

2. Everquest

3. World of Warcraft

4. Guild Wars 2

Thats all i can think of, and GW2 barley makes the list.  

1) City of Heroes

2) Hellgate London

3) Age of Conan

4) SWG

5) Tabula Rasa

1. WoW

2. GW2

3. FFXI

I haven't played significant enough time in any other MMO to include them on a list.  I've played less than 2 months of Rift, Aion, WAR, and AoC, and I've beta tested many others.  From what I've played of each of these, I'd personally rank most of them above FFXI on my list, but like I said, still not enough time in them to make a complete assessment.  

FFXI was my first MMO and second longest-played.  

WoW is my longest played by far: about 6 years on and off, from 2004-2010, over which time I probably had an active subscription for about 65-70% of the time.  

GW2 easily has the potential to eventually surpass WoW for me.  Many things need to change still, but the foundation for the game is far better than vanilla WoW's in my opinion, and that kept me for 6 years.  If WoW didn't require a subscription, I'd probably still log in every now and then and then possibly get hooked again.  With GW2's b2p model, it will always keep me logging back in and, therefore, has the potential to keep me even longer than WoW did.  

1) EVE

2) Shadowbane

3) LOTRO(pre-free to play)

4) EQ2

5) City of Villains  

I would like to note that the bottom 3 would be way down on the list under a list of single player games.

I dont think its fair to judge older games against newer. First it was a different generation, different tech, different gameplay mechanics... So i'll be posting two top 5 lists. One will be of the golden era of MMOs which ended with WoW imo and the other will be Post Wow Era stuff.

Golden Era: 

1. EVE Online

2. SWG Pre-CU

3. Everquest 

4 DAoC

5. Ultima Online

Current Era:

1. WoW

2. GW2

3. Lotro

4. Rift

5. SWTOR

1. Lord of the Rings Online
2. World of Warcraft
3. Dark Age of Camelot
4. City of Heroes

LotRO wins by a small margin due to the kinship (guild) that I was in.  Early WoW was so much fun but the community and guilds didn't match LotRO (pre f2p).  DaoC was the first MMORPG I spent a significant amount of time in -- I don't think I could grind levels today like I did back in the early days of DaoC, but there are good memories there.  Not a big PvPer today but I really enjoyed RvR and the loyalty to the side you chose (alliance vs horde doesn't even come close).  CoH (pre f2p) is for the many, many characters I created though I ruined the game for myself by making so many and redoing the early content over and over.

1. SWG
2. DAOC
3. EVE
4. Saga of Ryzom
5. EQ-OA

1: SWG pre-curb

2: Planetside 2

3: EvE Online

4: Darkfall online

5:Face of Mankind

1&2: My first two are SOE games despite having boycotted them for many years until the release of PS2, it just goes to show they can make a decent game when they want. I'm currently playing PS2 now that the cheating has died down (not saying it's gone it never will be), the game is alot of fun to play in an outfit.

3:As for eve I left after they changed the war dec system because too many people were crying about being attacked in empire.

4: A great game with excellent pve and PVP opportunities, it was just the horrible grind that turned me off.

5: What a game, great idea with an excellent faction system and so much going on. Unfortunately there was only one dev running it from his basement in Berlin and a bunch of s**t GM's that were utterly corrupt to the majority of players detriment. The company which published the game seemed to have no idea what was going on or just didn't care. This game could have been one of the most popular MMORPGs of all time but it was just left to rot in the gutter.

1. Ultima Online

2. Asheron's Call

3. Star Wars Galaxies (pre-NGE)

4. Eve Online

5. meh

For 5, there are dozens of game tied due to one or two outstanding mechanics or systems..unfortunately aside from those innovative systems the rest of the game tended to suck.