I keep games installed where there’s some more side-stuff to do later, I am convinced I’ll return them soon and never ever do.
Borderlands all of them, Diablo 2, Titan Quest, Lost Ark
I have replayed the class&loot games with little time to breathe, I like to get immersed in the guides and sidequests and having a mental map of the general loot drops for a month or two at a time, complete it then be done with it. (checking back in with a live service game every three-to-six months for that little bit of new stuff feels very unnatural to me). Starting a new class doesn’t feel punishing since the normal progression is finishing the story on 3 difficulties back to back anyway. Does that score as ky-often-replays or ky-never-replays?
Similarly, I have replayed Halo Reach alone immediately after finishing it in coop since I struggled to recall much from the game itself besides the cutscenes (An attempt to remember Reach 
)
I guess I need a little bit of gambling variety, in my head I count playing the really-similar releases as replays, like Costume Quest 2, Torchlight 2, Assassin’s Creed Rogue or the LEGO licenseds, years later.
I love Half Life 2 to bits but I wouldn’t return to the base campaign without MMod or something, I’d rather play custom maps.
I admire the chase for depth and mastery, but I’m a poser, the only games I can say I learned it properly like that is Dota 2 and some high-score chasing FPS: SWAT 4, Severed Steel and Wrack:Reclamation, technically replaying the same map, but not returning to them years later.
(I totally rewatch Youtube videos years later for comfort though)