Something you could always return to

I love a good many games and normally I tend to either stick with just one or multiple, I have little phases where I am obsessed with a game and then drop the obsession but still play the game.

There's a few games that I won't drop the obsession for be it games I've never played or have played, I'm interested to hear what are some games (If you play any if not that's fine) you have constantly bouncing around in your head?