The Sims, Counterstrike, and Halo are all predictably on the list, as is World of Warcraft. Not too unexpected-- these aren't just the biggest communities in online gaming, they're also four of the biggest games of all time. But most surprising, RuneScape also joins the others. It's a Java-based (as in played in your browser) MMORPG that's basically an updated, graphical MUD. And their numbers are very surprising-- they have 9 million free accounts playing, as well as 1 million paid accounts, which (if those were all separate users, which I doubt) would put them in range of WoW itself. Of course, a free game (that's played in a browser and not bought in a store) will always have a larger available playerbase than a retail game that has a subscription charge, but considering that 13% of all PC gamers have reportedly played RuneScape, that's a pretty big deal.
The other interesting, WoW-related fact that ActionTrip dug up is this: apparently PC gamers are still playing WoW more than four times as much as any other PC game. There's no question that since its inception, WoW has changed the face of PC gaming, and no matter what happens in the future, it's currently one of the biggest videogame communities in history.
[ via WorldofWar.net ]