Nice however there are some flaws with this build. I say this as I'm building my 2nd cab soon when I get some time.
Serial connection is better than usb because some games in usb there's a delay, this is detrimental to shooters etc.
The raspberry pi is not powerful enough to run all games without slowdown, I would use a more powerful pc with a basic gpu for 3d based games like tekken etc.
Finally the screen is a pc monitor and not a proper video games monitor with true scanlines.
Scanlines can be emulated but it's not quite the same, without a true video monitor like a wells Gardner then your skimping on your effort and final build which is great.