This is a series where the major themes of the Pokemon games compete on which one is the best. Disclaimer - this is all opinionated and for fun. Do not start any arguments on which theme is actually better, since that is a subjective statement. 

Categories I will do*: Wild theme (Hoenn won), Trainer theme, Rival theme, Grunt theme, Antagonist theme, Gym Leader theme, Elite Four theme, Champion theme, Pseudo Legendary theme, Mascot Legendary theme, Misc Legendary theme. 

*If you have another category you would like for me to do, please suggest it and I'll consider it. :D

I will be including links and embeded videos of each theme so everyone can listen to them.

I will also only be linking the most recent remaster of each theme. But if you prefer the original, choose that in the poll. (BW & BW2 do not count as an original and remaster, so both themes are added)

Round 2 - Trainer battle theme

Kanto 

https://www.youtube.com/watch?v=436SxbLz-OA

Johto 

https://www.youtube.com/watch?v=nwmaVNEYNEY

Hoenn

https://www.youtube.com/watch?v=uX6zM0bLvmc

Sinnoh

https://www.youtube.com/watch?v=FdFJHhzZ_Bg

Unova

https://www.youtube.com/watch?v=cWfP71MQusI

https://www.youtube.com/watch?v=5dIQ3sjlb40

Kalos

ORAS followed by DPP then XY

Maybe because I played ORAS most recently, but I really like the music at the moment

You could also do Best Villain Team Boss Theme

I knew I was missing something, grunts and antagonist. Thanks!

I really love the ORAS theme. I love all Hoenn music actually cause I started with gen 3 but for some reason I absolutely love Johto's theme. Idk why.

HG/SS Kanto theme
It's one of the few themes I feel that HG/SS didn't butcher.

As much as I love Unova, I must admit that Hoenn got this one

Unova wins for me, really epic, intro reminds me of a Champion theme.

I might do non-battle themes after. Not sure. There's a lot more of them and depending on the success of this series (I expect it to get more popular once I hit the Antagonist themes) is when I'll make up my mind.

It becomes more complicated too. So we'll see. I am considering it though.

Remember that gen 1/3 (Red/Blue, Firered/LeafGreen) has a different arrangement for many recurring themes, compared to gen2/4 (Gold/Silver, HeartGold/SoulSilver). It's not just made first for gen 1; then touched up in gen 2, then taking advantage of GBA capabilities in gen 3 and finally DS sound in gen 4. HGSS might sound closer to FRLG because of the non-8-bit sound, but it's actually a remix of the gen 2 one. This is very noticeable in the wild battle theme, although in the trainer battle theme, the cool chromatic "bumblebee" sound from gen 2 was removed in gen 4, so it sounds closer to gen 1 and most of all, gen 3. Just a random sidenote.

My favourite versions then, of the Kanto trainer themes, are the GSC/HGSS versions of it. I do like Sinnoh's battle theme more though, so that gets my vote.

Edit: I think actually the bumblebee sound is still in the HGSS games as well, after putting my iphone into my ear. I'll have to listen to it with better equipment to really hear it. Never noticed it before.