I buy whatever interests me.
I put 'em down 'cause I like to just completely devour a game and decide whether I want to keep it or sell it when I'm done provided I hadn't already made that choice already.
I normally blow through the one off games ( Conan The Barbarian, That Bourne Identity game, Afro Samurai, Brutal Legend etc) I know I can finish with a solid week or so worth of consistent gameplay while saving the marquee shyt (Borderlands series, Batman Series, Witcher Series, Fallout series etc, Lost planet, Dead space etc..) for when I've reached a point in my backlog to where I can play that one title in the genre and progress throughout the series similar to what I'm doing now with BorderLands 1. I'm on the DLC, then I'll jump into two and the presequel before the year's out.
Provided I don't die randomly, I've a chance I'll make a significant dent in my Backlog this year since I'm ontop this Current Gen's games that interest me which leaves me room to finally start last gen games I've still in the plastic. My major problem is buying alot of these games fresh off the bat, like for example The latest Fallout.
I ain't touching that shyt until I play Fallout 3...and I got all the DLC for that...then I'm gonna play New Vegas...with all that DLC and by the time I finally get to the latest one, it's either on Sale or I can cop for free. That's my problem. Was looking at Quantum Break the same way for a minute but now it's the upcoming Doom game.
I'll play 'em all eventually and enjoy the fukk out of everyone one though.