Oh man, I was playing a good amount of SC2 but I want somebody to play with, instead of playing with random guys I don't talk to at all. A couple of times I played with a friend while talking through skype, and that was fun, and I remember that SC2 and W3 were extremely fun playing in LAN years ago, but it doesn't seem very fun when it's just strangers.
Around 2 days ago I first played Hotline Miami, and man, it's really fun. Makes you feel like a super badass, although you can complete all of the levels in around 6 hours (although there's replayability because it's really fun to replay levels in itself, and you get new masks (which aren't like tf2 hats, have a significant impact on gameplay) and weapons on top of that). Been playing Super Hexagon on iOS when I have nothing to do and no access to the computer, although I'm not very good (best I can do is 45sec in Hexagoner :/), and I played Sleeping Dogs a few weeks ago and that was the best open-world game I've played. I play Civ 5 when I'm in a strategic kinda mood, too, although the addictiveness of that game wore down after the first 40 hours.
My favorite game of all time, however, is very different from these- Mount & Blade: Warband. Man, do yourself a favor, check it out, it's extremely awesome.