How suitable RubyMotion for iOS game development?
I was not able to find CoreAnimation topics in documentation, but as I've heard someone was able to use cocos-2d with RubyMotion.
If you have some useful information which you are willing to share, I would greatly appreciate this!
If you are willing to program your game completely programmatically, RubyMotion is a fine choice. There is no appreciable drop in performance and every C library and API is available to RubyMotion. Using motion-cocoapods you're even able to include CocoaPods and you can also include Objective-C libraries.
The one issue you may run into is a lack of RubyMotion-specific tutorials and documentation for games.
EDIT: I successfully (with help) recreated the Sparrow game engine demo in RubyMotion:
https://github.com/jamonholmgren/demo-sparrow
It runs beautifully.