As far as I know the original Xbox emulators out there aren't fast enough to run any commercial games, and it'll be a long time, if ever, before playable 360 emulation is possible. Emulation is very complex and inefficient, even emulators such as Dolphin that run Nintendo Wii games need comparatively very high end hardware to deliver playable performance.
Can't really go into any more detail than that on the forums as it's technically considered warez.