Super Mario Odyssey. it's my favorite mainly because I think it's the one that gives the biggest sense of adventure (which is something I really appreciate in games). In this game, exploring every nook and cranny of the worlds is really satisfying because there will always be something to find, and I also love the incredible variety that the Cappy transformations give to the gameplay and how there's so many creative challenges that make use of said transformations. While the game is not as tight as the more linear games, there's still many challenges that put your platforming skills to test.
Also, Galaxy 2 > Galaxy.