Personally, World of Warcraft is my choice. Yes, it can be a time sink if you choose. But since I have stopped playing hardcore a couple of months ago, I like hoppin on for 15-30 mins at a time, doing a few quests, levelling a bit, messing around in the auction house or doing some dailies. Sure, I can blow 8 hours on it if I want, but if I want to just kill some time or break up the monotony of the day, I can do that no problem with WoW. Just don't get hooked... cause then you won't have to worry about that job anymore. *sly grin*
But if WoW isn't your thing go with Lego Star Wars or Lego Indiana Jones. The levels take 10-15 mins a piece, cool music and all those characters you loved from the movies... in lil Lego format.