Sorry for disappearing for so much time guys, exams week and work are killing me! >.<
So, I saw something about Unreal Engine 4 and I think it's a good idea, indeed.
And @Xpand, do you know where to get some tutorials for learning how to program for this engine? I want to learn something 'bout it too.

Oh, and other thing: I remember that zero told me something about using C# to build some parts of his code. If possible, we could use the XNA framework for porting it into Xbox Live, can't we?