Any MAME fans out there? I think it would be a natural addition to someones gameroom that already includes pachinko and pachislo.

Don't know what MAME is? MAME is the 'Multiple Arcade Machine Emulator', an open source application that lets you run the games of old including Pac Man, Dig Dug, Joust, Burger Time, Spy Hunter, and more (currently supports over 2966 games!).

I'm looking to build a MAME cabinet for my gameroom. It'll run off a modified XBox using an X-Arcade two person joystick.

You can run MAME games off your PC as well. There are versions available for Windows, OS X, and Linux.

More info:

MAME:
http://www.mame.net/

X-Arcade (controllers)
http://www.x-arcade.com/index.shtml