At OnlineMBA there is a lot of online gaming statistics that reveals, among other non-MMO related things, that 94% of MMO subscriptions are to fantasy games. The rest are the other genres, like science fiction (EVE Online, etc.), Social games (Second Life) and real-combat / modern time simulators.
“It’s no secret to most of us that the MMO genre is largely dominated by fantasy games, but it is always interesting to be able to put a number to such things. Fortunately, many of the most highly anticipated games coming over the next few years are decidedly non-Fantasy, possibly marking a change for the genre as a whole.”