Thoughts on some themes that were mentioned by others here:
- Black version of Opelucid: Partly agree. I wouldn't say it is downright bad, but I prefer the White version, no contest.
- Gen 5 low health music: This was an interesting concept but it got annoying after a while, especially when it happened in battles which had really awesome regular music.
- X/Y Gym Leader theme. Partly agree here too. I don't think it is bad, but it isn't super great either. I really prefer the Successor Korrina theme which is basically just a variation/remix of the Gym Leader theme, find it below:
Hulbury: Yeah, this one is quite annoying.
Solaceon/Pastoria: Partly agree. Some parts of it is fine, other parts are just plain annoying. I remember being annoyed by it when I did all of my traditional breeding in D/P/P.
...
I thought about this subject for a bit and remembered some more music I’m not too fond of. Unsurprisingly, all of them are from the Johto games. Mostly from the Kanto part of the games.
First some battle themes. I don’t like the Kanto wild Pokémon and trainer battle themes in the Johto games. They just sound so boring. Neither of them give me any feeling of excitement or fun, they just bore me when I listen to them. If anything, I think they amplify the feeling of boredom I get when I play the Johto games, especially the awfully bland Kanto part. The wild Pokémon and trainer battle themes in Johto are fine, but I find the Kanto themes to be really boring. However, I really like the Kanto Gym Leader battle theme in the Johto games. It slaps hard, and I actually prefer it over not only the Johto Gym leader battle theme, but also over the original theme from the Kanto games.
Then there are some route and city themes as well.
I don’t like Route 29 in HG/SS. The original in G/S/C is fine, but the remake version does this weird thing where it slows down on a few occasions, which completely throws of the rhythm for me. It feels like they made it way to pretentious for a first route in the games, I prefer the original from G/S/C.
Dragon's Den in G/S/C. It feels like they were way too ambitious with this one, the Game Boy soundfont just couldn't do it justice. The remake version is much better, thankfully.
Then there’s one, which plays in far too many Kanto cities and towns in the Johto games (especially in G/S/C). I think the original version is just plain boring, but the HG/SS version is actually okay. Not good, but it works. It doesn’t bore me at least.
There’s also this one which plays on several Kanto routes in the Johto games. It bores me a bit and it does not give me a feeling of exciting adventures and exploration. Ironically, it really manages to capture the feeling of boredom I get from exploring the barren wasteland that Kanto is in the Johto games. I prefer the original version from the Kanto games over the Johto version of it.
This one had some potential to be epic, but I think it is too short and it loops too much to the point that it becomes more of a chore to listen to. I don't get this feeling from any other Pokémon League music, the other regions managed to have much better League music than Johto.
To end this on a more positive note (I know this is the wrong thread for that, but I wanted to say it here anyway), I still think there are some good music to be found in the Kanto part of the Johto games. I really like the Johto version of Lavender Town, I prefer it over the version in the Kanto games. I also think HG/SS absolutely nailed it with Cinnabar Island, and they did very well with Route 24/25 too.