I'm working for one of the major WAR fansites, so I suppose I'm biased when I say I'm looking forward to Warhammer Online.
That being said, I'd say there's such a thing as a successful MMO, but as for "good" that's entirely subjective. Some people like the thrill of open PvP that EVE has to offer. Others like going to a dungeon and slaying bosses that WoW currently has the market on. Different people like different things.
MMOs in general, however, need to take a hard look at development best practices. More than any other game genre, MMOs are plagued by multiple delays, cuts, and testing issues. Worse yet, the excuse is "That's how it is in MMOs". I don't want ot be an armchair dev, but I work in the tech industry and I wonder about the project management of some MMOs, which end up screwed because of bad development timelines (Vanguard is a good example).