RetroArch is a multi-emulator front-end including consoles up to PS2 and Wii. 3DS, Wii U, Switch, etc are currently *not possible* on Xbox.
Retro Pass is a simple frontend for RetroArch running on Xbox. The UI is similar to that of the Game Pass / My Games & Apps section of Xbox for a familiar feel.
PPSSPP is a free and open-source PSP emulator.
DuckStation is a free and open-source PS1 / PSX emulator.
Flycast is a free and open-source Dreamcast emulator.
Allows you to stream your PC games to Xbox! Developed and maintained by Elix!
Transfer files wirelessly on your local network!
DevilutionX is a source port of Diablo and Hellfire that strives to make it simple to run the game while providing engine improvements, bugfixes, and some optional quality of life features.
Sonic Time Twisted is an unofficial classic-style Sonic the Hedgehog fangame.