For this project, I created a step-by-step video on how to assemble the arcade console, load the emulation software, map GPIO buttons to USB, and install ROMs.
I'm using RetroPie for the emulators and Adafruit's Retrogame executable to map GPIO buttons to USB. RetroPie is great because it works with many different ROM files.
I've also included a 3d printable case so that you don't have to drill holes in the electronics box. (See project file)
Here is the GPIO pinout diagram for joystick and button wires:
And a pinout diagram for the joystick:
*Edit* Images of the completed wiring were also requested.