Wow, I thought I would be the only one to say that Gen 5 had the best overall music. I loved how chaotic and offbeat several of the tracks were (Vs. Neo Team Plasma; the legendary Pokemon battle theme). The heartfelt "friendship and maturity growth" song. The gym battle music (I forgot that B2W2 had each gym do a different take on that!; I loved Marlon's elevator music!). The Elite Four's deep, cerebral battle music. The end credits theme.
Uhhh...other, non-Unovan themes! Kalos's gym battle song rocks! The song that plays during the flashback is really heartbreaking. For nostalgia's sake, I always really liked Johto's Violet City theme. It stands out so much from all the other cities' themes. ORAS's Vs. Archie theme is so good, and Wally's battle theme was so surprising when I first heard it. The song that plays when you encounter Cynthia as a Champion, but not her battle theme (that piano, though!). Guzma's battle theme is really unique. For the newest games, the gym battle theme is obviously a crowd favorite. I also really liked Rose's battle theme, Bede's battle theme, as well as the Battle Tower fight theme. So basically I tend to like anything that's really quirky and breaks the rules of convention.