I believe The Beatles: Rock Band came the closest to being perfect. Eveything about that game was just beautifully done and the only things missing was Pro Drums, an option for Keys, and a few more Beatle songs (Hey Jude, Strawberry Fields Forever, Yesterday etc. etc.)
Maybe Tetris? Such a simple concept, and it’s one of the most popular games of all time.
Minecraft for similar reasons. Even if it has become more complex in recent years, the core of it is just…you can break everything and build anything. It’s hard to say that isn’t a perfect sandbox.
More personal opinion though, maybe Super Mario Odyssey. Just incredibly polished and varied with an amazing movement system.
Tetris is a game that just doesn’t get old.
It’s really you against your previous self, rather than you against the game.
It’s the same reason why I enjoy Mini Motorways so much!