Hm, the best MMORPG that I've played is
Face of Mankind. It's a game completely driven by non-NPC's, taking place in the 21st century (if I remember correct).
It's a great game (which everyone else in this thread tells you about their game), which I hope you'll look into or try.
Second would be
The Saga of Ryzom, a quite different fantasy game with unique razes, other then the usuall human, dwarfs, elfes, gnomes et cetera.
As many people has posted webbased games, which I don't really consider as MMORPG's, I'll add my favorite here too. It's called
Utopia, and I guess many of you have heard of it before. It's a fantasy strategic teambased game which goes on for three months before they reset the servers. Huge alliances which fights in wars all the time, and conflicts between different kindoms in the alliances. Worth a try. Completely free (as in free beer, not open source), but the downside is the huge abuse of ads, which you'd block obviously.
The unofficial Utopia IRC server is irc.utonet.org.
Paranoid people live longer.