Cataclysm: Dark Days Ahead, Dwarf Fortress. Highly-replayable, open-world and they keep being developed, so when you come back, there's new stuff.

Skyrim, Fallout 4. Same idea, but the modders have added a lot of content.

Some of the city-builders, like Tropico 5. I play for a while, get tired, uninstall, but tend to come back, because the game is replayable.

Chase the Sun and Nova Drift are action games that I have spent some time away from and then come back and played. Nova Drift has seen regular development.

Pinball sims. I think that one can only play so much pinball, but I find myself thinking "I'd like to play a pinball game" down the line and reinstall.

I think that most of the games have some common characteristics:

• Didn't live-or-die based on their technology or graphics, because they're invariably obsolete by the time I've come back.

• Need to be highly-replayable. I've played games with story, like Fallout: New Vegas but I don't really go back to play them for the story (though I'll concede that specifically Fallout: New Vegas does have multiple paths to explore). They can't be appealing because of a surprising or tense plot or a plot twist.

• Often see continued development or modding, so there's some reason to go back and see what's there (though pinball would be a notable exception...you don't go back for new content).