CityVille is a webpage based online game produced by Zynga, the same company which produced farmwille. It was realeasd on November 2010. It is the most popular web game at present. The game is ralated with Facebook so it has a very convinent channel of getting players. It attracts 2.9 millon players on the very first day of releasing,  in 12 days, the number grows to 26 millon and the players reach a peak of 70 millon in a mouth. It is an amazing achievement in game history.

I think the game is popular because it's really interactive with other players. The players can become neighbours with their frinds on facebook. You can visit your frinds city and do some thing to it.
Playing this game makes the player feel they can control the world, they look their city in god's view and have to be responsible for their citizens. Players have to build more housees and shops. And players also need to take care of their neighbours situation.

CityVille is from the classic game SimCity. Zynga is the company that made this game, they made a lot of great browser-based games. The one before CItyVille is FarmVille. Farmville used to be the number 1 popular game until Cityville released. They are hoping to ern money from these "free" web games.

The main compectitor is FarmVilly and a lots games all over the internet.