There was a time when I just could not do this. I used to play a single game at a time. I would play nothing but that game until I was done with it, and if for some reason I did leave a game unfinished, the next time I wanted to play it, I had to start from the beginning again.
I just do not have the time to waste on doing that these days. Additionally, my tastes are an order of magnitude broader than they used to be. I tend to jump around from game to game as a rule these days. PC gaming makes it easy, because all of your games are just a couple of clicks away--no discs to swap out, shelves to keep organized, et cetera. If I play one single title exclusively for a week or two it's something I'm deeply absorbed in, like Dishonored, recently, or Diablo III earlier this year. So, I find myself with a lot of games back-burnered, and I find myself picking up game saves that have sat around untouched for months at a time.
In the last couple of weeks I've gone back to Fallout 3 (9 months or so), Half-Life 2 (8ish months), and Diablo III (around 2 months). The last was just to see what the two major patches since August had changed, and to see if I still liked the game after some time away. Turns out I do!
Fallout 3. I love this series. Even set apart in time and space from the first two games, Fallout 3 carries over a lot of cool things in the world. It's really good, and I'll write more about it in the future. I can't decide how much of the side stuff I really want to delve into. I know I want to hit all of the main DLC bits, and finish the main quest, of course. After that, we'll see. It might be really tempting to move on to New Vegas.
Half-Life 2 I decided to pick up just for some more conventional FPS gameplay after going the stealth route through Dishonored. As no one needs to be told, it's a great game. I'm still just a meager 2-3 hours in, though. More will be written about this one, too, time comes to pass.