I like all the music, except for maybe Adek's Champion theme, too upbeat for a "final battle".
But, top favorites:
- All Plasma Themes (N's [Battle, Non-Battle, it all.], Geechis' sort of, Grunt Battle (favorite of Plasma themes honestly, other than one of N's non-battle themes.)
- WCS Kanto Champion Remix
- Cynthia's Champion Theme (New Key and Tempo)
Souryuu City: White Version (I've been playing White, when I heard this I just stopped playing and listened to the music for a while. It's got a melancholy; yet, peaceful feeling that I love about it. Kinda shocked actually that theme is in a Pokémon game). Heard Black Version's version of the theme. Not a fan.
EDIT: Relistened to Black's version of the theme. It's not bad, but still like the White version's of the song better.
- Gym Leader Theme (Especially on last Pokémon with the homage to the original Pokémon theme).
- Elite Four Theme (Didn't like it at first, but it quickly grew on me.)
- Low HP - Theme
- Generic Trainer Theme: Regular and Battle Subway versions.
There's more, but those are the standouts for me; that I can currently think of.