I'm not sure about the Jaguar port of Doom, but Sega of America did the 32X port and Midway handled the Saturn, PlayStation and SNES ports. The 3DO version was handled by some unknown developer who completely botched it. Lobotomy, Midway and Activision handled the Quake trilogy ports.
As I recall Carmack performed most of the engine porting to the Jaguar, even going so far as to write an optimized C compiler for its unusual architecture. Take a look at http://www.scribd.com/doc/470798/John-Carmack-Archive-slashdot-posts for some interesting highlights - the Jaguar stuff starts on page 26.
A bit late on my behalf (128 comments since I checked yesterday... jeez!).
But excatly, Carmack has worked on a couple ports, and that is about the best example of how far he will go. His work across various platforms has always had my interest. His ability is awesome to say the least.
Unfortunately the world has changed, and trying to keep up is interesting as always. Although I believe Carmack has been and always will be more interested in pushing the technology to achieve something glorious in graphics. id's games have always been simplistic, and I don't believe this is a bad thing, which has helped him create even more beautiful games which lead to the engine being licensed out.
Now the licensed users have created some fantastic games which have become hits, adding complexity and flavour the the id engines. id's games are hit and miss for each person, just like some people like coke while others prefer pepsi or neither at all. Look beyond the fanboy action, and see the ability that is there.
Dare I say it, I would love to see something like Alice ported to the Rage engine. id's games have their place, and I only hope that maybe before Carmack retires that he gets a couple more engines in, and that the engines lead to some beautiful games (remember the first time you played Quake? or even Quake 2... simple game and pure quality).