I just finished Super Mario Galaxy from 3D All Stars for the first time. It's pretty incredible and just like I hoped, is waaaay better than Super Mario Odyssey, in my opinion. The only significant improvement the latter has on it is the controls/advanced movement tech (which is standout and almost single-handedly makes the game), and even then Galaxy is pretty great in that regard, but other than that, Galaxy beats it handily in concept/universe, visual art direction, purpose/focus, awe-inspiring charm/artistry/elegance, music, level design/progression, and satisfying challenge. Even the story elements, which I never would have expected from a Mario game, is nailed perfectly.
Odyssey has some cute gimmicks and moments of fan-service, but the aimless do-anything open world nature of the game and endless meaningless fetch quests are terrible, in my opinion. Even technologically, the 10 year surface-level advancements that are to be expected is barely even anything noticeable.
The only gripes I had with Galaxy were that the occasional "special" levels that 100% relied on motion controls were tedious skills to adjust to (they were kind of a fun break from the norm in a way I guess), I'd occasionally run into this thing where Mario would get locked into repeatedly running around in a circle after making an awkward input (not sure if this is specific to the Switch version-- it feels like it's related to the tricky control nuances of moving on a small sphere), and like Odyssey, I still really dislike this clunky idea of progressing by collecting some arbitrary number of achievements that open up new areas (still not as bad as in Odyssey where the achievements don't even involve fully beating levels). It's more elegant and less lifeless to do that part the old way, where there are required and optional paths that can be taken from beating one level after another, IMO. "Just do this until you've done it enough to progress" just feels stupid to me.
Peak Mario is now Super Mario Bros. 3, Super Mario World, and Super Mario Galaxy for me in no particular order. Haven't played 64, but I'm a bit skeptical (might do that one next). Also intrigued by Galaxy 2, but from what I'm hearing about it, I don't really expect to like it quite as much as Galaxy 1.