Yeah! that's right! the best music that makes your blood boil!

I think to me it's Kingdom Hearts II

Megaman X

Metal of Honor

I like Metal Gear,Kingdom Hearts 2 like you mean,and Crash Bandicoot =)

i like gundam super metroid and FFVI

Drakengard II, Ace Combat (all of them), Grandia II, Legend of Mana, there are to many of them, actually :p

FFX, Wild arms 5(I heard the theme and went carzy), KH2 and kh1, also COM.
Devil mat cry 3. I can't think of anythink else.

probably kh1+2, zelda, ffvii (main theme is AMAZING). thats all i can think of

To me, the best battle theme is the regular boss battle theme from FFIV.

chrono cross

Digital Devil Saga Series, no doubt. The random battle music
in that game was better than the boss music in many other
games. Also the boss music is addictive. Too bad its often overlooked.
But Kingdom Hearts II is a close second. Especially the song the 13th dilemma.

mario rpg had the best music (enemy, mini boss, boss, culex theme (aka final fantasy IV's boss theme, forrest maze, rosetown, smithy's themes, pipe theme, yoster's isle, marrymore, booster's tower, volcano, etc.) i've heard in awhile.

final fantasy III has REALLY good music. ffVI, ffVII, super mario 3, river city ransom, super mario world, jet grind radio, street fighter 2 and 3, parasite eve, etc. have good music too.

I've always found the Metal Gear Solid alert track pretty good, also the battle music from FFX always gets stuck in my head for some strange reason.

I love the battle theme in FF7 where you're supposed to catch Chocobos, great classic....

Shadow of the Colossus. Each song fits each colossus perfectly and really sets the mood for the battles.

liberi fatali (FFVIII or FFIX I forget)... even though its not a battle theme persay but there's a fight going on during it...

Devil May Cry 3! (^_^)

I hate DMC 3 battle music though I like the Game.

I would say FFT Zodiac song that thing always kept my mind buzzing. Safer Sephiroth's music and Wild arms Boomrang flash. Also FFIX you are not alone is good.

Gilgamesh's theme and Boss Battle from FF5. Or actually every battle music from Final Fantasies. Shadow of the Colossus has also great battle themes, especially against the last Colossus. Godly. I want more Kow Otani music! :(

Pilot wings

i love AC3 Electrosphere music =P

it's very good to air combat games

Skies of Arcadia and Shadow of the Colossus really got me into the battles. They had some epic-sounding music.

Ace Combat Series (except AC3 too electronic but there are some good ones too for example the execution)
Halo 1 Truth and Reconciliation Suite
Final Fantasy series

Legend of Zelda, OoT

Last battle with Ganondorf. Gold.

Shadow hearts 1 to me had some of the best game music...and yes KH2. Bully has some sweet tunes too.

Half Life 2- the part in City 17 when you have to "get to the horse." In the console:

playgamesound song_16

I call it "To The Horse."

Or practically any music from Half Life 2: Episode One. Great stuff.

playgamesound ep_song_8
(meet the Zombine!)

Along with the hospital shootout music. Awesome track.

The Battle music when fighting as or against Lord Blazer in Wild Arms 2 always gets my blood boiling

Tack on "Splinter Cell: Chaos Theory" for me. Great music, epically in firefights.
"Burnout" games also have great soundtracks ("Revenge" and "Dominator").

Earth City from Halo 2 was really good, and I also find some of the music in C&C Generals was perfect battle music.

I just beat Shadow of the Colossus the other day. And I must say that the game had some of the greatest music I've heard, especially during the Colossi battles.

I really like the battle music in SMRPG, as well as Paper Mario. I also love the final boss battle music from FF: Crystal Chronicles. :3~

1.FF VIII : Don't be afraid
2.FF XII : Esper battle (I like the feeling that we're fighting with god)
3.Xenosaga EPIII : Battle of your soul

As for me, I am rather fond of the music from the Shin Megami Tensei series, as well as Skies of Arcadia, Earthbound(Nat Cole, anyone?), and Shadow of the Colossus. Paper Mario and it's family also have awesome music... But, the most immersive soundtrack for me, would have to be every now, corrupting, immersing sound from Silent Hill. Every game feels like it could be you, journeying through the depths of your mind.

Or mebbe that's just me. ;P