What to play, What to play

Over the past couple of weeks, I have been contemplating what I actually want to completely play through, or even play extensively; instead of just playing it for a couple of minutes and then realizing I actually don't want to play it. I have been playing Perfect Dark Zero, Oblivion, and Half-Life, on and off, but not to the extent I would like to play. Basically, what I am saying, is that I want a new game, but I honestly don't know what I want. Any suggestions?