I could never get bored with Civilization 2, or Lords of the Realm, or Close Combat 2, or Age of Empires. And I put a lot of hours in, between 10 and 18. I'm not sure that Candy Crush is anymore fun than those games were.
Oh my god. And Starcraft, and Axis and Allies, (original) DOTA. I was even a WOW player back in the day before I got fed up buying expansions. Man, the hours of productive time I wasted...