• Halo 2
• TLoZ:OoT
• Half Life

I can’t deny that nostalgia has to do with the first two fossils in the list, though I still maintain that I like them more than their latest counterparts in their franchises.
Not Half Life though: it was ~15 years old when I first played it, no nostalgia there.

Still, between the many games I would gladly build a monument to, those are games that I can play beginning to end without getting bored, annoyed or burnt out (as long as you allow me to use the Ship Of Harkinian randomizer for Z:OoT, otherwise replace that game with Perfect Dark ig).