Going by the statistics recently released by stat-tracker AppData, social gaming company Zynga's December-launched `CityVille' has overshadowed the same creator's `FarmVille' as the leading Facebook game in the world.

Boasting nearly 67.4 million `active users', CityVille - the the free-to-play, city-building simulation - has beaten the 57 million `active users' figure of the earlier top-notch Facebook game, FarmVille. The astounding success of CityVille was quite evident right at the outset, when the game pulled in 290,000 unique players with a day of the game's December 2 launch.

Speaking in overall terms, active users of Zynga's games on Facebook, the gaming company - credited with popular titles like FrontierVille, MafiaWars, FarmVille, CityVille and others - comprise a total of almost 269 million.

Moreover, the Zynga games hold six of Facebook's `top 10' most used apps, arranged on the basis of monthly active user counts. Of the remaining four spots, Takeoff Monkey holds two with its Phrases app; and developers Causes and Social Graph Studios have one app each.

According to recent reports, the total valuation of Zynga - which was worth approximately $5.27 billion in October 2010 - has surpassed the figures of its brick-and-mortar game-developing rival, Electronic Arts (EA) - the comparison being made on the basis of Zygna's shares of stocks as valued on the secondary market SharesPost versus EA's public trades on the Nasdaq market.