I was surprised how great the Fallarbor theme sounds in these games. It used to be my least favorite town theme in Hoenn, but now it's one of my favorites.
In addition to Fallarbor; Meteor Falls, Gym Leader Battles, Lilycove, Slateport, Oldale, Southern Island, Route 113, Diving, Mt. Pyre, Zinnia, the Zinnia Battle and Victory Road are probably the themes I liked the most from the game. The Frontier Brain Battle theme is also great, even though I actually prefer the original version to that one (I also must say that I strongly dislike that it is used in that awful Battle Maison...)