I think most people familiar with the original Xbox hw (like people working on xemu :)) take offense when you say it's just a PC. It's PC hardware, but nothing much is shared with the "IBM PC" architecture-wise. Even the software side is very different. It's not running a customized version of Windows, but the Windows kernel. One stripped down to 256kb, including the boot up animation and sound. That design for example required that a lot of things get linked into a game's executable, like network drivers and the entire TCP/IP stack.

If it were that easy, we'd have had a wine pendant for Xbox binaries 20 years ago. Cxbx is pretty much the wine approach to Xbox emulation and it's far from perfect.