Doom is a fine milestone for an OS that intends to have graphical capabilities. Maybe Doom in text mode for other OSes :P

It's a known quantity, and doom has been ported to everything, so it shouldn't be too hard to make work either (he says, not having done it).

An OS that can run Doom is clearly capable of graphical interfaces with user interactivity, and maybe sound (although sound would be easy to leave out).

Yeah, that's perfectly fair. I raised my question because it occurred to me this kind of sells the operating system short. In other words: even DOS could run Doom (with some help with a memory extender I guess, which is a technology we can all very happily not worry about anymore).