Less than a month after its launch, Zynga‘s CityVille launched less than a month ago, but it’s already reached 61.7 million monthly active users, surpassing FarmVille and establishing itself as the world’s most popular game.

Combined with FarmVille, this means Zynga has a total of 261 million monthly active users of their Facebook apps, dominating social gaming in 2010. Zynga’s games, both CityVille and FarmVille are free to play, but users can spend real money on virtual goods, which have brought in between $500-$700 million in revenue this year, as reported by RWW.

Also this year, it was announced that Zygna’s second market valuation is now bigger than industry giant EA’s.