Why not?
They're too powerful to be emulated, accurately and at full speed anyway.
But it looks like deoblo85 wants to use real XBox's - did you want emulators FOR the Xbox? There is an Xbox MAME build, and no doubt there are several other emulators. IIRC Micro$oft have been typical b@stards about such things tho (I think they require a modded Xbox to run), so they can be hard to find on the web...