When someone is looking to get into game emulation in this day and age, RetroArch is likely the most common suggestion. It's a front-end that utilizes Libretro cores that open up the ability to emulate old platforms -- from Atari to NES to MSX to disc-based platforms like Dreamcast and PSone. RetroArch isn't too difficult to get up and running, although it might require a bit of patience from those who haven't dabbled with game emulation before.
One of the biggest reasons RetroArch stands out of the crowd is because it supports a wide-range of platforms on both ends of the equation. Even Windows 95 and PowerPC-based OS X is supported! It might surprise you that even consoles themselves are supported, like the Wii, Wii U, Switch, PSP, PS Vita, PS2, PS3, GameCube, Nintendo 3DS, and soon, Xbox One.
It's surprising that such a new console could be manipulated to run old games to your heart's content, and we owe a lot of thanks to Microsoft for simply not having so many restrictions put in place. The major caveat with this latest endeavor is that you'll need to sign up with Microsoft as a developer, and then enable devmode on the console itself.
Effectively, using RetroArch on your Xbox One does not break any rules, as Microsoft allows you to pull off every step without any questionable actions. We can't help but draw a parallel to the original PlayStation 3, which allowed you to install Linux on it (for a time, anyway). Putting RetroArch on a console is so much cooler though, and it's even more impressive that it can be done pretty easily.
Xbox One might be the only game console out of the big three so far that will not require you to jailbreak anything in order to run RetroArch. All it will require is that you put your Xbox into Developer Mode - MS officially supports this and allows it (https://t.co/56ctxarF1u).— libretro (@libretro) December 28, 2018
If you were using RetroArch on an older platform that's not a PC, you'd undoubtedly see improved performance when moving over to the Xbox One. As for those with a PC, RetroArch on Xbox One could be used mostly for convenience, for a better couch experience. The Libretro Twitter account also mentioned that FreeSync support is a useful reason to use RetroArch on Xbox One as well, provided you're using a compatible display. RetroArch on Xbox One is probably the only way you could play emulated games with FreeSync and not require a PC, and while the games will not have a hard time running on modern hardware like the Xbox One, frame-smoothing can still add a notable improvement to the fluidity.