I have over 300 games on Steam, I'm not sure I've even played half of them. Of the ones I have played, many were only for an hour or two. I have more unplayed games from other sites, and even a few on disc.
I'm terrible for impulse buying games. I'll pick up almost anything that's cheap and looks vaguely interesting. I'll subscribe to MMOs and stop playing after 2 weeks. Even amongst the games I really enjoy, few last more than 20 hours before my attention wanders to something else. At the start of the year I decided to limit myself to buying 1 new game a month, but only kept it up for 3 months before buying a big stack of games in a sale. I don't think I've played most of the games I bought then.
So I'm setting myself a challenge. I'm not going to buy any games, no matter how cheap they are, how good they look or how much RPS rave about them. I'm not even going to download free games. I'm not going to try and force myself to work through my backlog in alphabetical order or finish games if I'm bored of them, but I'll give every game I play a fair chance. I'm going to keep a (brief) log here of what I'm playing and when I bought it (if I can remember). Maybe someone will find it interesting.
Now Playing: Skyrim - Preordered, playing since release.
I'm surprised by how much this has gripped me. 44 hours might not be long compared to the playtimes some of my friends have racked up, but it's longer than I stuck with either Oblivion or Fallout 3. I think I've still got a way to go to catch up with Morrowind, but I'm not close to getting bored yet.
I've been playing Blood Bowl, ArmA 2 and Solium Infernum regularly for months or years now and don't plan to stop. Multiplayer gaming seems to hold my attention in a way single player does not, although my stamina for competitive shooters seems to have disappeared since I got bored of TF2. I spent 6 years playing EVE regularly and very little of other games, I half want to find another MMO to replace it (although I've had no luck so far) but I also feel I don't want to sink that much time into a single game.