I'm not active at all with any other game since years. For "relaxing" when XOL is DOWN I spend time with Red Alert series (all old versions & add-ons)
as for FPS, Im probably trying Wolfenstein demo soon, got DL already. Here are the past favourites:
Amstrad864, there was this one sidescroller game where you catch ghosts (dont remember the name) Ridiculous but fun (1984)
Doom, Doom][, Duke nukem 2, and the FATHER of 'em all:
Duke nukem3D (I even got portals last year that make gfx in "HD")
Have you guys any clue how much of the fun stuff in UT99 that originate from this game, wow ;=)
Drove through all of NFS except 5(porsche edition, I hate the sound of porche cars) up untill the Drifting that I didnt like...
All things played, I think most of us will still play UT99 on XOL in 10 years time, just the gamespeed will to 20 % !

I notice, nobody is mentioning half-life(or whatever this whole thing is...never tried it at all)
peace out