LibGDX is one of the best engines I’ve ever used, works on almost all platforms, and performs twice as fast as cocos2d-x in most tests I’ve done. You can use any JVM language you like. Here’s a 13 part tutorial in Java, and here’s a bunch using jruby. There’s a good skeletal animation tool that works with it here, and it has baked in support for tiled TMX maps as well. The ui framework is awesome, and it has a scene graph and actor style API similar to cocos2d scenes, sprites and actions. The community is awesome, updates are frequent, and the documentation is good. Don’t let the java part scare you, it’s fast, and you can use jruby or scala or whatever you like. I highly recommend it for 2d or 3d work, it supports both.