Undoubtedly the best music ever in their complete glory (All of the tunes in 1 go):
Age of Empires 2 (Star Wars Battlefront is even more awesome to both of these soundtracks playing instead of Star Wars music.)
Conquerors Expansion (Personally, I like this one better)
Obvious one to add to the list:
Ace Combat 0:
"Hey buddy... You still alive?" --Solo Wing Pixy (Obligatory, Extended version like you'd hear in the game)
Glacial Skies (Similar tune, but an awesome opening game 1st mission theme. New mercs joining a battle.)
Round Table, Part 2 (Incoming Aces vs The Demon of the Round Table)
Ace Combat 4:
First Ace Combat 4 mission (Always a good "You're important right now"/"Last Hope" kind of theme to hear.)
Ace Combat 2:
Blow Away (This has an awesome Arcade sound to it. I miss Arcade sounding game themes. They always have such an upbeat tune that makes you want to keep fighting.)
Night and Day (Always reminds me of my livestream channel for some reason. Raiding a mining colony. Low altitude fun. Another fun upbeat tune.)
Rising High (High energy craziness. I think you also have to stop a shuttle launch to this tune.)
And some classic Starcon 2:
Introduction ThemeStarbase Commander Starbase MenuHyperspaceQuasispace (DOS) (They are 2 different versions; both are great. But the DOS version I still like better)
Ur-Quan (Scary how most the time, this is the first thing you hear when you start your game, just as you get started.)
Spathi (A staple of the UQM franchise)
VUX (One of the best tunes in the game)
Arilou (Then again, they also place 1st.)
Yehat (...You know what? They all tie for 1st place)
Unreal Tournament:
Mechanism Eight Necros (Always amps me up and always associated with awesome clusterfuck battles)
Razorback (Orion's Barricade and Monestary always come to mind with this theme)
Skyward Fire (CTF - Lava Giant. 'nuff said. Best associated with it's classic UT99 version. But this is a good remix.)
Hyperblast (Another remixed version of the classic UT99 version's theme. Awesome nonetheless. Yes, you fight on a ship inside of hyperspace to this theme.)
Forgone Destruction (CTF - Facing Worlds. Best CTF level ever. Sniper's paradise.)
Run (Just do as the song says; or say hello to a rocket or some bio sludge to the face.)
Ending (Plays when you collect a trophy)
Sonic Generations:
Stardust Speedway (Vs. Metal Sonic. Not bad music for a boss fight. Can you beat Hard Mode in less than a minute?)
Casino Night Zone (Truly an awesome remix of the classic Sonic 2 music and stage. That pinball game is addicting as hell, especially the music.)
Doomsday Zone OC Remix (Wish they had this song on this game. Still listing because of it being awesome.)
Final Fantasy:
-6-
Searching For Friends (By far, one of the best tunes in the game. Always makes me flashback to the 90s watching my brother play this game. It was awesome then, still awesome now when I play.)
Treasure Hunter (Locke's Theme) (Awesome music to start the game with. Too bad you don't hear this theme too often.)
-X-
Challenge (Extended version. I love this boss theme. Really fitting near the end)
Fight With Seymore (Could have been a better battle, but the music still rocked.)
Assault (No better raiding music than this.)
Summoned Beast Battle (Just about the final battle in the game, and also against the spirit of Penance in the International version (Bastard is bigger than Sin, and many times nastier). Epic ending sequence music.)
EDIT:
Now that I come and think of it, I really love battle themes. Pretty much my soundtrack to Revelations; provided it happens as described in the Bible in my lifetime.