There's such a huge difference when comparing a console sports game to an MMO pc game.

Of course competition is good for anything, as it promotes improvements, but for a console game, it doesn't matter to a player that if a new game comes out that games player base suddenly gets cut in half.

This is most definitely an issue to MMO's, where I'm sure a large part of their appeal actually is the amount of people play them. It's not desirable to feel part of an empty community, especially when that is one of the largest aspects of these games.

People will always lean towards playing the MMO's with the most players, as it gives them options in their play experience. This is one of the many reasons WOW will dominate their competition.