Framework : Cocos2d/Cocos2d-x

Cocos2d/Cocos2d-x is the framework I use for programming.

Its an  open source framework built over openGL.

Reference links: 

http://www.cocos2d-x.org/

http://www.cocos2d-iphone.org/

Cocos2d-iPhone is wrapper written in Objective-C where as Cocos2d-x for iOS and Android is written in C++.

So if you know C++, you are good to go for develop your game.