Replaying games I enjoyed is not a rarity at all for me, and in fact some sort of habit.
Especially some sort of PC games that are basically MADE to be replayed over and over (i.e. UFO, Jagged Alliance 2, Civilization, Mount & Blade, Master of Magic, Heroes of Might & Magic, ecc).
That said, in recent years it HAS to be XCOM 2.
According to my save file tracker I played something like 19 campaigns with the game and most of them were from start to finish, too.
I don't think any other single player comes close in terms of hours invested on it.