What are the most underrated songs from the Pokémon games? Honestly people sleep on the X and Y soundtrack. It has so many hidden gems, like Anistar City, Elite 4 theme, Geosenge Town, and the Poké Ball power plant. Other underrated songs (in my opinion) are Seafolk Village from sun and moon, Opelucid City white, and Route 210 from diamond and pearl.
Fire Island Volcano, from Pokémon Super Mystery Dungeon. I mean...32 seconds in, it's on. It's the best dungeon theme in the entire franchise. Also, Arceus' theme from Pokemon Ranger: Guardian Signs. Most people think of Arceus' kinda weird battle theme from the main series games when they think of Arceus, but it's theme from this is, in my opinion at least, far superior. It's regal, atmospheric, and vaguely chilling - the kind of thing you'd expect from a creation deity. Plus it sounds like something out of Columns.
I don't hear a lot of people talking about Colress' theme, but I love that techno jazz he has going on, its one of my favorites. Other things that I believe are truly under appreciated is the entire sound track of Pokémon Conquest, primarily because its an underrated game. Its very ancient Japanese inspired music, but it is still an amazing sound track.
Route 203 from D/P/Pt. It's a pretty upbeat song, and honestly it's a song that makes me want to run to it.