I have a love/hate relationship with crusader kings 2. it's such a master peace, and I can get hooked for weeks. But when you loose your empire because your disgrace of a son is a drunkard and a craven, and no one will vote for him... that's when I flip the table and don't play it for a long time.
Honorary mentions:
Dying light - I love dying light, but I just can't play it alone. I can only have fun with it if I'm playing coop.
Pillars of eternity - both games are SO GOOOOD. Still, too long to get engaged in more than one play-through