Roguelikes.
Roguelites.
Chess.
Deck builders.
More broadly, games with different narrative choices (eg: Witcher 2 has two mutually exclusive middle acts).
And also more broadly, games with different mechanical choices (eg: many RPGs).
There's also games where the process itself is fun (eg: Tetris).
Also, as many humans have imperfect memory, after enough time has passed a game may feel fresh playing it again. It may also land differently playing it at a new stage in life.