From my limited understanding the Dreamcast also has one of the simplest architectures of that generation (since Sega learned from the monstrosity that was the Saturn) which I would think would make it a good target for homebrew. The GPU was also an early PowerVR design so maybe contemporary mobile GPU expertise can be leveraged instead of trying to target the Gamecube or PS2's proprietary architectures.

Of course the OG XBox is probably simpler to port a PC game to since it basically _was_ a PC so it doesn't really count in this discussion.