The following are the best themes in their respective categories. If you disagree, you are wrong.

Best Town themes: Virbank City and Royal Avenue

Best Route themes: Sinnoh Route 216 and Sinnoh 210.

Best Dungeon Themes: Vast Poni Canyon and Giant Chasm

Evil Lair themes: Rocket Takeover HGSS, Silph Co, Deep Plasma Frigate and Sinister Aether Paradise (Sorry for the large amount here, Hoenn and Kalos are the only bad ones and Galactic and N's castle just missed out.

Rival Themes: Silver, Galdion and Hugh

Champion Themes: Literaly the only bad Champ themes are Alders, Dianthas and the League Defence one.

This is fact.