I have a tendency to get very hooked on games. As such, as much as I love computer games, I've been avoiding MMORPGs including WoW. I've known people who neglected children to play Everquest (or EverCrack, as my friends and I like to call it), and I'd rather not go down that route if I can help it. I get the feeling, however, that in a few years the only computer RPGs worth playing will be online, so I may wind up drinking the Kool-Aid eventually. (Or, maybe I'll just stop and read a book or something.)
The only one I've ever been tempted to play online is Diablo II, and I've primarily been hesitant not just because of the addiction factor, but because I've heard there's a lot of jerks on Battle-Net, not unlike that guy from the South Park WoW episode who kept killing everybody's character-- except, in addition to killing them, they'd rip off all of their nice, hard-to-get equipment, too.
EDIT: I just found a list ActionTrip did of
The Ten Most Influential RPGs of Our Time. Look who's number 1.