Just went through all the forums here, and find out there is no mobile phone topics, I noticed there is a sub-forum: Mobiles, Handhelds and PDAs, but that's under Software.I think at least we can open some forums to discuss Android, IOS, Windows Phone etc. This is from OS level. And we can also have some forums to talk about devices. Like iPhone, HTC and Nokia etc.
As far as I know, Java is not good at gaming area in desktop. As you only provided two choices, I suggest you to take a look at XNA and WPF. XNA has a very easy to use framework to build DirectX based game while WPF provided a easy way to create fancy 2D UI, though WPF support 3D, but the performance and experience is good enough.I am not saying Java is not good as .NET, personally, I also spend time on creating android applications.Hope this can help you.