Nope, though I do try. Reasons?
-If I'm not having fun, not gonna bother.
-More my fault, but if I got a new game before finishing the older one, I might not get back into it.
-I play more multiplayer based games nowadays, and those can't really be "finished". Hell, I got maybe halfway through the Bad Company 2 campaign, so I sure as hell didn't spend 30 hours on single player.
I have been trying to go back to games I haven't finished to beat them, but that's kinda hard if you haven't played them in a while, you forget controls, what you were doing, what the hell the story is, etc..