I have only completed 5 games in the past 3 years (bioshock, halo 3, brawl, mario kart, zelda) yet alone replay any! I play multiplayer far more than single player though.
It took 3 of us to help you though Halo
Games I've Replayed
Halo 1/2/3
FFVII - Regularly replay this
FFVIII (although never actually completed it, I am a bit of a chronic restarter (I have gotten to the end several times realized I missed something and started)) all over)
FFIX Same as FFVIII
FFX - Periodically replay this
GOW
Fable
Day of the Tentacle
Dune2000
C&C
Red Alert
Doom (replay from time to time)
THPS3 Played through quite a few times. (well with all the characters tbh)
MGS2 - bloody dog tags
GTA3/Vice City/ San Andreas
Unreal Tournament (the original) got a quick blast a few months ago.
Quake4 I wanted all the play through achievements, not sure I ever got them tbh... I think I got board. Certainly I wouldn't bother now.
Dead Rising.
DMC
Back when Half Life (the original) came out, I bought it on the PC, but at the time I was playing games for 10 days then returning them to get another game. So on the 10th Day I hadn't completed the game so I took it back. Years later I bought it for a fiver on the PS2 as I had vowed to complete "The Best FPS Ever" Played through the game with a massive sense of De Ja Vous, When I got to a part I didn't recognize it was the final boss. I had literally played the game all the way to the end the first time and had I waited 10 min before taking it back I would have completed it on the PC.