Something that I have picked up on my travels, the best Xbox emulators are :-

286/386 - DOSXBox
Adam/Collecovision - AdamX
AGI Sierra - SarienX
Amiga - UAE-X
Arcade - MAMEoX
Daphne Laserdisc - DaphneX
Apple IIgs/e/c/+ - KegsX
Atari800/5200/130/320 - AtariXLBox
Atari 2600 - Z26X
Atari Lynx - HandyX
Atari ST - WinstonX
Commodore PET - VicePETX
Commodore Vic-20 - Vice20X
Commodore 64 - Vice64X
Intellivision - BlissX
Killer Instinct 1/2 - U64-X
MSX/MSX2 - FMSXBox
Neogeo/CPS/CPS2 - Kawa-X/FbaX
Nintendo 64 - Surreal 64
Nintendo Game Boy Advance - XBoyAdvance
Nintendo NES - FCEUltraX
Sega Genesis/32X/CD - NeoGenesis/Xenesis
Sega Master System/Game Gear - SMSPlusX
Sega SC-1000/3000 - SC3x
Sony Playstation - PCSXBox
Super Nintendo Entertainment System - xSnes9x
SNK NeoGeo Pocket - NeoPopX
PC Engine/TG16/CD/SCD - HugoX
Spectrum - Dreamspec (Doesn't work yet)
Wonderswan - WonderSwanX
X86 - Bochs