Not buy a single game this year, and clear my backlog of 50+ games (not including the humble bundle stuff I've purchased).
I have a Calculus II and our first kid in April, so my time will be greatly limited. So to be realistic, I'm equating what I spent to buy the game to the amount of money I'm willing to spend for entertainment.
Example: Deus Ex: HR takes about 15 to 20 hours to beat, main quest only. The game cost me $10 on some Steam sale a while back. I'm willing to spend 10$ to rent two good movies, or see a couple of matinee movies, or couple of six packs and few hours with friends. If I hate the game, or completely lose interest, I'll play for 4 or 5 hours before calling it quits and moving to the next one, officially marking it off my list.
Lately, it's been bothering me that I've essentially paid money just to have the title of a game added to a growing list.