Earlier quoted context omitted.
Honestly Quake 2's biggest feature was going open source. When I was porting Quake 2 to MS-DOS, I have to admit that it's the most I ever played of it. It really fell into Carmak's view that stories have no place in gaming. It's a shame Valve found a much bigger market than games, but it leaves the mantle for others to pick up.
But it wasn't the first id game to go open source.
And iD did a great job of writing modular and portable code.
It was really exhilarating to get it running on a different platform with essentially no real changes, other than platform code and initially removing the DLL support.
Thankfully DJGPP had progressed far enough that its DLL support works great.