i want to do games for android & windows with a 2d game framework and i dont know what is the best thing for this 2015.

I personaly use cocos2d-x. I tried several engines (but none of those mentioned in this post) and this is the first one I am satisfied with (mainly because of its good rendering performance).

I personaly use cocos2d-x. I tried several engines (but none of those mentioned in this post) and this is the first one I am satisfied with (mainly because of its good rendering performance).

in cocos2d-x the documentation and tutorials are good?, wich of the three languages is more used and have more tutorials and documentation?, is faster the development?

I'd recommend libGDX if you know Java or if you're new to object-oriented programming. It does a lot of the <subjective generalization>boring</subjective generalization> work for you and lets you create your game fairly quickly using one codebase that compiles to every platform that Java can run on (including browsers). Pretty bad ass if you ask me, and perfect for 2d games (I'm using it to make a 2d MORPG myself using the Kryonet library for networking).

But I'm a complete noob at games programming after taking a ~10 year break and having to re-learn everything, so don't take my word for it. Plus I've always been a Java guy because I'm a trial-by-fire kind of programmer, so I love (ie. depend on) its noob-friendliness. But I'm sure all the alternatives mentioned do just as well as libGDX, it all depends on what language you're most comfortable with I suppose.

Anyway good luck, it's a lot of fun. The first time I got my shitty Mario Bros rip-off to run on my android tablet I felt like a kid doing Hello World all over again. Good times.

Here are all the libraries I mentioned in case you're interested. It's probably best to use Eclipse unless you really know what you're doing when it comes to project file management and online repositories - the tutorial below explains how to set up Eclipse with LibGDX pretty well if you choose to go that route.

Eclipse: https://eclipse.org/downloads/

LibGDX: https://libgdx.badlogicgames.com/download.html

Kryonet: https://github.com/EsotericSoftware/kryonet

The Mario Bros tutorial I followed to learn the basics of Android rendering and input handling with LibGDX:

And you'll probably need this no matter what library you choose to go with:

http://developer.android.com/sdk/index.html

Have fun

I personaly use cocos2d-x. I tried several engines (but none of those mentioned in this post) and this is the first one I am satisfied with (mainly because of its good rendering performance).

in cocos2d-x the documentation and tutorials are good?, wich of the three languages is more used and have more tutorials and documentation?, is faster the development?

API documentation is the most useful part of the docs. There are tutorials how to set up new project and about few more topics, but many of them are outdated so you will have to learn mostly from the api (which is quite ok). The community (on forums) seems to be quite big though (I have read that 50% of top-selling games worldwide are using cocos2d-x, not sure, what exactly this means). I am not sure, which language is used most (I am not realy interested in anything else than C++), but I think, that c++ is the most used with cocos2d-x.

Is faster the development? I cant realy say. To me, all engines seem quite similar (because I am used to build my own framework on top of stock engines I use). I wouldn't say, that the API is in any way excelent - I have seen way better APIs, but as I mentioned, this was first engine I was able to (almost) finish a game with and not run into performance problems or fatal feature limitations.