I don't think it's necessary to muddle it up though. There's something to be said about a vanilla quake session that hasn't translated into pretty much anything else out there since or before (except maybe Quake 1 or 2).
As great as vanilla Quakes were upon their release -- Q1, Q2, Q3 -- I've played these games and I've played their maps. Playing other maps with this IOQuake mod -- this has brought life back into Quake 3 Arena for me. It's good I actually have a really good reason to dig this classic out of my vault, when I'm in a mode of "What the hell am I going to play?" I need some sort of kick-ass MP-fix. I mean, hell -- I like GoW PC MP, but God -- nobody's playing it online! GoW PC got uninstalled today, BTW -- I just can't take the lack of servers going for this game; it's just...sad.
I think a lot of people's perception of Quake changed namely with Q3A vs. UT wars, when those two came out in the same year. For most people, UT was basically the MP-game everybody wanted Q3A to be. As good as Q3A was, UT just offered more, out the box. Personally, I don't know how you can go wrong w/ either a Quake or Unreal game; that's just me, though.
I hope most people played Quake 4's MP -- which is basically Quake 3: Arena gameplay on the technically awesome-looking Doom 3 Engine. In other words, it really rocks. I don't think it ever took off like Q3A did on the MP-side, since Q4 is a SP and MP game, so I think many played it for just the SP; while Q3A was just made for MP so people are just gonna' play that Q3A for the MP.