Borderlands! It has all the taste of MMO-like questing and looting with none of the calories of a mandatory internet connection and getting harassed by strangers! Friends entirely optional! Buy now!
I played the shit out of Borderlands, as did my dad, but when I got Borderlands 2 it was mainly for him and I didn't touch it for months. When I finally got around to trying it, I was bored within minutes. Then, after finishing my master's thesis I really needed something to take my mind off things, and the Borderlands 2 treadmill was ideal. So I played to level 20, which was when I finally got fed up with "go here, kill that" and juggling loot around, and stopped playing it entirely. It's a nice game, but enjoying it depends on either tolerating or ignoring the fact you're on a treadmill.
Currently I'm mainly playing Hearthstone, even though there are plenty of other games I'd like to play more, but I won't allow myself to spend big money* on anything now that my student financing has dried up. Oh well, there's always bundles!
*To me that means any one game that's five euros or more. If nothing else, the astounding devaluation of PC games is pretty good for my wallet.