My games design teacher taught me something which always comes screaming back to me any time I want to buy a new games.
I don't remember the exact figure, but something like 80% of games bought don't get completed.
The problem I have with completing games is that I'll play it, enjoy it, take a break after a few hours and then end up playing FFXI or TF2. Not to mention I have been really busy this year. So whenever I bought a new game, there was a nagging feeling that I really should be doing something else. Something less fun than playing games, making games.
Just looking at my pile of 360 games, I need to complete:
Assassin's Creed
Final Fantasy XIII
The Saboteur
Metro 2033
I don't have the same problem with PC games, strangely. The only games I haven't completed on my Steam list are Prototype and Silent Hill: Homecoming and I probably never will. Every so often I tell myself that I owe it to the first three games to complete Homecoming. Each time I get to the police station, I give up. Prototype I got onto the last few days, and then my laptop broke. Don't really want to play the whole thing again.