Original Xbox, it doesn't exist yet. That's gonna be difficult to make.
It would have existed by now if there was enough interest in emulating it.
But the development interest just isn't there.
Why is it so hard to emulate OG Xbox? Wasn't that build using of the shelf parts?
In a 2014 interview, blueshogun96 (a developer of the rudimentary, unfinished Xbox emulator Cxbx) outlined four reasons why Xbox emulation still isn't a reality:
"1. The lack of people willing to work on such an emulator is the largest reason.
2. A big misconception is that Xbox is just a PC. It’s not. It is in it’s own right a console, with PC similar (not identical) hardware. The thought of emulating a console that was PC-like, with many of the popular titles having PC ports was not of interest to many.
3. While I’m at it, I’ll mention that there’s also a large misconception that all original Xbox titles are also on PC, which is also untrue. When they bring up examples, they are speaking of Xbox’s most popular (and IMO mostly overhyped) titles, such as Halo. Other games that were exclusive to Xbox didn’t get much spotlight, and to this day, many are still unheard of. i.e. Azurik: Rize of Peratha (my favourite), Gun Valkyrie, Panzer Dragoon ORTA, Shenmue II, Jet Set Radio Future, Sega GT 2002, and many more titles I can’t think of off of the top of my head. If you bring up those titles, chances are they’ve never heard of them. Sega did many exclusive titles, and very few of them got PC ports, like Crazy Taxi did.
4. Even though there are those who assume that Xbox is easy to emulate just because it has an x86 processor and PC like hardware, experienced emu authors will often stay away from it, knowing that it’s a huge undertaking. Think of it this way… Is a PC easy to emulate? Is emulating x86 easy? Is writing a VM easy? Is emulating an NV gpu easy? Absolutely not. There are those who write theories of how “they” would do it… if they could. And there are those who are able to make implementations."