I'm going to be honest. None of either Galaxy's musics really jumped out at me. Don't think I can remember any full song from either game, aside from bits and pieces of the main themes. It all mostly just sounds the same to me.
Very good list, indeed. And I imagine it would be a hard one to make, as I am struggling myself in trying to mentally think of my top ten favorites. I know for a personal fact, though, that if the SMG games featured the style/quality of music as used in SM64 and SMS, I wouldn't adore them as much as I do. There is simply no question that the music, for me, made these games.
Back to your list.... I would say that Melty Molten (Galaxy) is my favorite. I love how Mario lands in that level just as the music kicks in. His landing reminds me of Superman's on Lex's sky island. Just awesome.
If I could add one to your list, it would be my current favorite Super Mario Galaxy tune, Nemesis Bowser. When I received my CD set from PlayAsia way back when, and this song started playing... Wow. I cranked the volume, and conducted/boogied away. Amazing stuff to be certain.
I love threads like this! I spent about 40 minutes listening to each song in its entirety. Great list! These two games have two of my all-time favorite game soundtracks, no question. As for ones that didn't make it...
Both credits themes are marvelous too.
As is Melty Monster.
And Bowser's Galaxy Reactor.
And Bowser's Galaxy Generator.
I'm with NoName--the music of these games really makes the experiences feel grand and majestic.