I like:
Return to Castle Wolfenstein
Wolfenstein: Enemy Territory
Soldier of Fortune series
Wolfenstein 3D, Doom 1 & 2, Blood, Quake 1 & 2
Call of Duty 1 & 2 (they are both pretty much the same)
MoH single player is very good.
Unreal II
Half-Life 1 & 2
FarCry
Don't like:
Unreal Tournament series
Halo
Most of Tom Clancy
Counter-Strike
FEAR
Quake 3 & 4
Doom 3
Prey