I believe Everquest was the first game of this format making WoW and all WoW clones in-fact EQ clones. I couldn't say with certainty as I never played it.
What I do know is the game description I just gave is followed by:
Having played both a great deal I can say that, on paper, the games look the same, but the execution of their similarly listed features makes the games night and day. (I'm talking about EQ back at its height, before WoW came out. You cannot compare today's EQ which has tried to emulate WoW in some fashion). There was nothing like WoW when it came out, so it can't really be a clone. EQ2 was pushed to release 3 weeks before WoW, but since these two fought head to head, they didn't really clone each other.
That is what I question the most, however: The execution. You could make a list of 10 features in an MMO, give the list to 3 different game studios, and the three games could be radically different.