Final Burn Legends is an Arcade emulator for the original Xbox. It plays and supports over 2,700 games. In this video (via The Games Shed) they give you a demo of the games packed in the great Arcade emulator. Keep in mind, there are about 100 + Emulators for the Original Xbox which vary from Atari, Super Nintendo (SNES) to Nintendo 64 (N64) and PlayStation (PSX) so be sure to give those a try as well.
To be able to install emulators on the original Xbox you must soft-mod it. Afterwards, you can start installing ROMs and emulators via FTP, we provide all the tutorials in the links below.
Final Burn Legends (v1.12) (Download from EurAsia.nu)
Final Burn Legends is a port of Final Burn Alpha 2.99.07 to the original Xbox. It also includes parts of FBA-XXX Pro 1.29. Support for over 2700 games. Some games are not playable anywhere else on the original Xbox. New in this rel: Optimized each original Xbox binary compiled per instruction from 'freakdave' over at emuxtras.net. Added 2 wide icons for those of you who use them.
How To: Install ROMs and Emulators on Original Xbox via FTP + Download Links