Mario Odyssey 9/10 Main game story, not all moons.
Late to this and avoided all spoilers, played all prior main games going back to Super Mario Bros on a Nes as kid in the 80's, so I've seen the evolution of the Mario platform series first hand, mostly within a couple years of the games release, or on release with Super Mario World and Mario 64.
I loved Mario Odyssey, I feel it's the true sequel to Mario 64 I was waiting for after Mario Sunshine being more limited location and both Mario Galaxies the smaller globe Worlds got old for me quickly, but Mario Odyssey was exactly the freedom and larger open World style I wanted from a new Mario game.
I loved the changeable costumes, the little craft that you travel around in, loved all the little details. I think I prefer this to Super Mario 3D World on the Wii U which I also liked more than any of them since Mario 64. I know the Switch version of that adds a new Bowser game to 3D World so I might have to get that on Switch too.
Going in with no spoilers or guides some of the secrets were awesome, with some genuinely surprising level themes and bosses.
I'll probably try collect all moons as it's a great pick up and play game for that purpose even after the main story is over.