I'd like to see a sequel to Quake 1. That game was probably the most original of ID's games (besides Heretic/Hexen - which were Raven)
The environments were so cool in that game, from high-tech bases to medieval castles, to weird otherworldly "runic" designs with a lot of metalwork. Add the ambient style of music, and the lovecraftian monsters - it really made an eerie experience. A sequel could be amazing.
I was disappointed how Quake 2 went back to all base/installation as its environment - it felt like a combo between Quake and Doom, but more like the latter - the Weapons were almost the same, and the enemies weren't even as good as Quake or Doom. Shame ID continued the Q2 part of the series instead of the original.
i totally agree with the quake I comments, i played the hell out of that game....beat it over and over and over. If you never bothered, Trent Reznor created a soundtrack for it, but it was sadly never implemented into the final game. I would check it out if you interested in his take on Quake.
As far as Quake II goes, i totally loved the singleplayer and multiplayer. Quake had MP mods, but quake II blew the whole genre of modding games wide open. Also, the soundtrack is my all time favorite, well actually the only game soundtrack I can remember without hearing it. You could play it straight off the CD, and i remember rolling in my first car jamming it loud as hell.....yeah....dork.
lee