Hmmm, completed quite a few games. Some go unfinished due to them being poor. Games i have completed (that i can remember)
Arcanum
HL + HL2/EP1/EP2
Portal
Deus Ex 1/2
C&C all of them
Mechwarrior all of them
Total Immersion Racing - (that is a rare one, a racing game that MADE me finish it in 1 sitting)
CoD4 - Done that in 1 evening/night. Gripped me till the end.
GTA 1/London1969/2/3/VC not SA (too boring) and 4
Sacred
Unreal Tournament (didnt do the others, they were a let down)
Quake all of them
X - Well i got to the end of the story
+ loads of the old FPS style games (Doom, Duke3d etc)
These days most games are all about the looks. Everything has to be 'real', that means blurry graphics with **** loads of bloom all viewed through a used coffee filter. I really want the games to move away from this. Its just a lame distraction from the fact that they havent bothered to work on much the gameplay.