Spot on, I was quite obsessive about going for 100% completion as I played through but since I finished it I haven't touched it, not even for multiplayer. But maybe it's more like a film or a novel, I personally wouldn't go straight back and watch or read something I had just consumed.
Maybe it's a hopeful sign of where games could be going though, that they can contain an affecting storyline and characters you actually care about (characters full stop you could argue), that a story can be told through a game in a way it can't in other mediums. I read an argument that Red Dead could have been even better if around a third of the 'filler' missions had been cut, I'm not sure if I agree with that but if games are ever going to recognised as 'art' then something like Red Dead is a good stepping stone.
Saying all that, the game I've played most this year is MW2. Screw the artistic merit, the multiplayer is like crack, especially when a few mates play regularly too.