Actually the game itself marked a real progression in the MMORPG genre, Blizzard effectively took a concept that wasn't working that well in the gaming industry and made it fantastic, so you can't really fault them for that... HOWEVER...
Since then Blizzard have become lazy little so and so's and insist on re-releasing all their old titles with the next number in the numerical sequence slapped on it and the only thing they've changed is to up the graphics, e.g. Diablo 3, Starcraft 2 - and I can just envision World of Starcraft even now.
Try moar Blizzard.
EDIT: I don't actually play WoW