Thanks to an independent developer, Quake II has perhaps become the oldest game to have been updated as a Universal Binary on Mac OS X. In order to use this software to play Quake II, you will still need a full copy of the game to grab some of the core game files, and I think the full source from id Software themselves (scroll down about two thirds of the way) might do the trick. While the source code there is listed as a PC version, I think the core game files you need to use this UB enabler for Mac OS X will work just fine. If anyone else knows better, feel free to sound off and list a link, if you could be so kind.
Either way, it sounds like setting up this software is pretty simple, and in no time you too could be fragging aliens circa 1997!