Good job!
I see that your first picture is from Rocket League, i ussualy play rocket league using the steam controllers :) It would be really nice if the steam controllers could work with it.
Luckily the video processing libraries provided by Intel/NVIDIA/AMD are cross platform (Win32/Linux). So the arm specific video processing code for the RPI is a different can of worms, the rest of the client (window creation, polling for input, etc) should be able to support Linux and X11 generally.