I picked up Quake 4 on the cheap and decided to replay Quake 2 first. I used to play a lot of Q2 SP back when it came out as it and Half Life were the only FPS I had. Also played a lot of Fallout 2 and Red Baron 2 as those were about the only games I had when I first got into PC gaming back in 97/98 so I replayed them many times.
I went from an IBM 200MHz (NonMMX) to building my own and overclocking Celeron 266 and 566 to 400 and 850, respectively. I still have my 200 running as a mp3/divx server and my Voodoo 2 SLIs/TNT1&2 are living in a box in a closet in case I ever feel or need to build an old system to run older games.
I played the first level a bit before checking out some texture mods to bring the game a bit more up to date. While I didn't mind the polygon explosions, I just can't resist modding stuff. I ended up using Quake 2 Evolved but also found EGL both of which update the particle system, textures and shaders, etc. Either work just fine but I think EGL sped up the enemy speed and I didn't feel like seeing if this was tweakable back to the original setting.
Before playing way too much Counter Strike, I got into MP gaming by playing Q2's Action Quake mod. Not sure what other Q2 mods I might have tried but there sure are a lot out there though I'm not sure how active they still are. No plans on any MP play this time as I'm focusing on SP. I'm not too much into MP these days except an occasional game of Co-op (Joint Ops, Ghost Recon, Raven Shield, etc.) or the rare team vs team round (BF2/BF2142, UT2K4, etc.)
The game still held up well. The level design and gameplay are still fun and the classic run and gun/key find elements flowed well. I don't think I've played this since 2K but I still remembered parts of the levels though I had forgotten the overall order of the maps and got lost many times as well as ambushed. The jail section has always stuck in my mind as the soldiers' mutterings added to the creepy atmosphere. The world is still as brown as I remembered it :) which has set me up for a nice color shock when I replay its contender Unreal.