Ultima Online, my first MMORPG and by far my favorite. I have played or beta'ed almost every MMORPG released until about a year ago.
Ultima Online is the ONLY computergame that has ever produced a serious adrenalin rush in me. From getting hunted and killed by PKs for the first few years to "grow up" and form a group of PK hunters later on is without a doubt the best computergaming experience in my life. It has also resulted in friendships, still active, with people from all over the world.
I wish that some of the newer generations of MMORPG had chosen to mimic UO over EQ. Unfortunately we are left with a lot of games that "owe" more to EQ than UO. A bad bargain in book.
That being said, there has been games that has made some things right. DAoC is a good example, the PvP in that is probably the best in the genre at the moment, but DAoC has issues of balance that flaws the good PvP system. It also has ToA. Trials of Atlantis, an expansion that introduced PvE elements that made you do Masterlevel quest for 10+ hours at a time in huge groups of people who contributed little besides more lag.
One game that WANTED to make everything right was Star Wars Galaxies, it failed miserably, despite having one of the best MMORPG designers at the helm, Ralph Koester aka Designer Dragon from Ultima Online.
IMO SWG is the biggest MMORPG dissapointment so far.
World of Warcraft is probably the MMORPG that has gotten most things right (at release) so far. So many things are well thought out and you can feel that the designers has had serious experience with the other MMORPGs out there. The
"Craftsmanship" is incredible. Now they have to do well in the ongoing development of the game and they have what will probably be the standard for years to come.
WoW is also chockfull of humor, one thing that is somewhat absent from a lot of the competition..
damn..got longer than i anticipated