I am a former WoW player myself. Played just over 2 and a half years and was a hardcore raider for the last year and a half. I understand the question and I will give my 2 cents on it.
It depends.
Certain franchises would be smash hits while the traditional Star Wars, Star Trek, Lord of the Rings, and other lesser known franchises such as Fallout and Fable will bomb because they don't have the history of multiple generations growing up on playing their games and the critical mass of younger fans to make it an ongoing successful venture such as the World of Warcraft. Star Trek, Star Wars, and Lord of the Rings are contemporarily viewed as good movies to watch, but their fans are scoffed at as nerds and socially retarded to a certain degree by their irrational fandom. Case in point, those who speak in Klingon.
MMORPGs based off of any Nintendo franchise (Mario, Donkey Kong, Metroid, Zelda, and Pokemon) would rival WoW quite easily. Similarly, I could see a Halo MMORPG doing well, but that is about it.
The main problem I see is, and I cannot verify it 100%, the fickle nature of console gamers due to the constant lineup of new releases year in and year out. Console gamers are spoiled in this regard. Console gamers have a certain degree of expectation when it comes to new games. The success of an MMORPG relies on killing this expectation and sucking you and all your time into its world.
When WoW came out in 2004, I noticed a significant drop in the quality of new PC games. What was the bleeding edge with Diablo, Fallout, Half life, StarCraft, Counter Strike, and on seemed to really be hit hard by WoW sucking up all the gamer dollars and time.
This leads to another question, do MMORPGs monopolize the gaming market to the extent that the quality and quantity of new games is much lower?
I believe so. Just consider the PC games released from 1996-2004 and compare that to the PC games released from 2004 until now. Much less in quantity and quality since WoW invaded.
