Day one for me. Its just so frustrating they aren't putting in Galaxy 2 so that we have all the main games in the series on one console. It's kind of inexcusable really, a bit baffling they didn't do it.
Also don't get why it's only a limited time release. It's gonna be a pretty big title, almost a must have for Switch owners.
I remember Sunshine was a bit disappointing to me as there wasn't a ton of variety in the levels as it seemed to ditch the usual Mario tropes of snow, desert, lava levels a bit. But really keen to play it again as it looked beautiful on the trailer and the special stages were the ground work for Galaxy and a lot of Odyssey.
Galaxy will always be amazing. It felt to me like the perfect modern interpretation of the old 2D games. Pure platformer, and done with such perfection.