One person's work is another person's play. Or to put it in game terms, one person's grindfest is another's idea of good fun. This appears in WoW, where to me, the endgame raids become a grind all their own, and don't forget your dailies... But to the vast majority of users, the game
starts when you get to that level (well for me, it began when I hit WotLK, but that's a different discussion). There's always something a bit more to strive for (ie, that next piece of gear or that title) either Raiding or Arenas.
In EVE the differences in what people think is fun, and what people think is work is very apparent. I think Mining is a bore. I like Industry. I'm indifferent to the PvP and Exploration (yes, there is a niche for the exploration minded). Others think anything is boring if they aren't blowing each other to bit in fights that take large alliances months to recoup from monetarily. Others like the pseudo-relaxing aspect of sitting there semi-afk mining away at rocks all day, and don't intend to really branch into anything else.
The single most important aspect of an MMO is for the developers to have a clear vision of what they want to do with the game. When a developer loses sight of that vision for their game, that is when an MMO begins to flounder. It is impossible to please everyone, and attempting to do so will only lead to a subpar game. It IS possible to please general subsets of people, as EVE and WoW clearly show, but it is impossible to get them all.
Also what needs to be addressed is the idea that the number of people playing an MMO determines its success or failure. Obviously when you have millions of people playing your game, you've done it right, but when your core base isn't in the millions doesn't mean you've failed. I haven't played Darkfall (I actually just now noticed they've recently added a free trial, so I'll probably check it out), but from what I've seen and heard it could be considered a successful game. As long as the developers stick to their vision for it, I don't see any reason why it shouldn't continue to see long-term continued growth -which I believe is the very definition of successful for an MMO.
And more on topic... I don't really care about who belongs to who so long as I get that 40k MMO sometime soon.