Most popular Facebook games: From Bubble Witch Saga to CityVille

[Every other week, Gamasutra examines the most popular Facebook games according to monthly active users, looking at the top titles and developers on the social network to see who's attracting or losing players.] The trend of the season for Facebook games, bubble-themed puzzlers, is still going strong as King.com's Bubble Witch Saga became the fifth most popular games on the social network -- the first time in a while that a non-Zynga release broke into the top five. Though Bubble Witch Saga appears to take inspiration from classic arcade titles like Puzzle Bobble/Bust-A-Move, the game was one of the first of its kind to make it big on Facebook, and its audience of 19.1 million monthly active users is far bigger of most clones in terms of audience size. Bubble Safari, released recently by Zynga, is the only bubble game with more users -- 29.5 million players, more than half a million more than what it had two weeks ago. The only game on Facebook with more users is Texas HoldEm Poker, which has grown by 1.2 million players to 33.3 million. Zynga's other games on the site aren't performing as well, however: CityVille, once the biggest game on the site not too long ago, has lost nearly 4 million monthly users and is now down to 24.3 million. And the developer's Draw Something app, which interacts with the popular mobile game, shed 2.3 million players and has fallen to 18.8 million total, which put it behind Bubble Witch Saga. Zynga's CastleVille lost 1.4 million users, too, and now has only 17.8 million total. You can see the full list of the top 20 Facebook games along with exact monthly active user counts below: All charts and data are courtesy of Facebook application metrics and trends site AppData.