That's.. how many? 8/ 9/10 mentions of Roxie's gym? Really, the music there seems too- artificial- for a rock band. Especially with the words in the background, where O and N are quickly sung in one beat, knocking the rhythm off. Cringe-inducing, to be sure.
Elesa's gym has some nice music, not too out of place but not flaunting the 'fashion show' theme. Steady pulse throughout, repeated refrain, accentuates the mood of the gym.
Gym leaders' battle theme has been remixed to epicness- much more dramatic than the original. Personally, I find that the shift in music at the last Pokemon gives it a 'final stand' or 'fight to the death' feeling, especially when the Pokemon is the most powerful and revenge kills just about every Pokemon on your team. And then you 1HKO it.
My favourite is actually the Village Bridge theme, complete with flute, guitar and enka (that's what the style of singing's called in Japan, thanks Wikipedia!). Wistful and reminiscent of a post-war song, mourning for good times gone, especially when you check up the lyrics. I'm surprised that nobody has mentioned it.