None of these are in line with your examples, but these are the first things that came to mind when I thought of "games that never get boring."
- Racing games like Forza - with hundreds of cars to choose from and countless options for customization, a new car is always available for me to test drive. I'll frequently fire up Forza Horizon just to cruise around in something that I'd never use in one of the actual race events.
- Sports games. I'm still playing NCAA Football '12. I love the dynasty mode - going through season after season, watching my players improve and move on to the NFL while I recruit the new players that will replace them.
- As mentioned above, Diablo and Civ are both good for hundreds, if not thousands of hours.
- Sudoku. Seriously. Whenever I'm bored of literally anything else, I pull out my phone and solve a sudoku puzzle. It never gets old.