Dragon Quest III- Adventure vs Mega Man 2- Wily Stage 1+2
The DQ3 music is fine for NES music, but it's up against The Best NES music Ever Indisputably.
Castlevania: Harmony of Despair- Ryukotsuki vs Splatoon- Calamari Inkantation
For extra context, imagine Super & me dying repeatedly while Eph tries to solo the fight during the 0.75 seconds Ryukotsuki is vulnerable every 30 seconds or so.
Kidou Senshi Gundam F-91- Act 12 vs Bastion- The Mancer’s Dilemma
Pretty easy.
Wild ARMs XF- Intrude Upon Happiness, Plunder the Future vs Pokémon Sun/Moon- Guardian Deities Battle
I actively dislike the Pokemon theme. Not the way I'd have gone for Hawaiian-ish music.
Vanguard Bandits- Dingdingding vs Ace Combat 04: Shattered Skies- Megalith ~Agnus Dei~
The realm of Fudo noms, I see. Megalith is... TOO over-the-top epic IMO, but Dingdingding is nothing special.
Baten Kaitos: Eternal Wings and the Lost Ocean- Survival From the Force vs Bloodborne- Gehrman, the First Hunter
Survival from the Force is great, it's "classic" Sakuraba but one of the best at doing that Sakuraba thing. That said, Gehrman is pretty unusual for boss music and quite effective at it, so sure.
Lunar Silver Star Story Complete- Go Go Go vs Tales of Xillia 2- If It’s For You ~Song 4 u~
The ToX2 track is pretty cool, and I like the main theme it has, but it feels like it's a lead-up to something, or some change-up, and it kinda doesn't go anywhere. Just repeats itself. Which is fine, it's still good, but the Ghaleon battle music is also quite good, so.
Final Fantasy VII- Anxious Heart vs Kingdom Hearts- It Began with a Letter
Letter seems like it'd be fine in context, at least, but a little TOO laid-back otherwise.