I am using cocos2d to develop iPhone game, however, it is just an 2D engine and developer is too flexible to use them - i.e. codes tends to be unmanageable.
Are there any more high level framework for game development, perfer using cocos2d?
Update: In the meantime Kobold2D was released. It's based on Cocos2D but adds more features like LUA integration or ARC (automatic reference counting) for easier memory-management. The features introduced by Kobold2D don't make it a much "higher-level" library though. It helps to setup new projects though and comes with lots of additional code and bundled third-party libraries.
Kobold2D v2.0.4 is out now as of October 2012.
Check out this resource, thorough article about the best iPhone game development frameworks:
There are a couple kits available for sale that provide starting points/frameworks that are built on cocos2d. Sites like http://learn-cocos2d.com and http://raywenderlich.com have great tutorials and point to these kits. Another good one which is being updated currently is the iphonegamekit.com which includes source and documentation for a rpg game or checkers game using cocos2d.