I wish they kept the Assault version of Star Wolf's theme for Smash the remix is alright but I prefer this version.
Seriously! I can not believe they removed this... Shame on them! I had it set to always play for that Star Fox stage on Brawl, because I loved it so much. The synthesized versions just can't cut it when we have this amazing live orchestral performance of it. If they return Wolf in DLC this track better come with him.
(EDIT: No, wait! The track IS in SSBU! Beat 20 Miis in Rival Smash!)
Otherwise, I'm a sucker for Melee's OST. So many tracks were orchestrated and I fell in love with pretty much all of it. But my favorite after all of these years if the Fountain of Dreams theme. Smashing! Live's renditions of all of the music is beautiful, too and I actually wish they'd just add them in the games instead. lol
I also love Brawl's theme, and SSB3DS/Wii U also has a theme that has really grown on me.