#10: Champion Theme (Pokemon Heartgold/Soulsilver)
This theme will always be special to me because Lance was the first champion I ever beat in Pokemon. Also, this theme is just pure, unadulterated awesome. You know you feel it.
#9: Akuma Battle Theme (Street Fighter X Tekken)
I haven't had this game for very long, but it's a pretty good game so far. This theme plays when you fight Akuma at the end of a Tekken character's Arcade Mode. Akuma has always been one of the coolest characters in Street Fighter, his theme has always been awesome, and this version of his theme is definitely the best, second only to the Oni version... possibly.
#8: Polygon Man Battle (Playstation All Stars Battle Royale)
This music is perfect for a climactic boss battle. The multiple phases in the music kind of seem to represent the different phases of Polygon Man's attacks, and the chanting in the background is pretty ominous and cool. Pretty badass, like you'd expect from a pseudo-Smash Bros. clone.
#7: Isle of Creation (God of War II)
Yes, this is technically more of the "main theme" of GoW2, but it plays when you fight Zeus at the end, so it counts. This song just gets you pumped for an extremely epic battle of gods, and the more you hear it in the game, the more excited it gets you for Kratos's rage-filled battle with Zeus.
#6: Twister-remix (The World Ends With You)
Technically, this is the only boss theme in The World Ends With You, as the songs used for other boss fights are used in later normal fights. This is also probably the best version of the game's theme song, Twister, even though you may not notice much differences from the full version of the song, other than what's obvious. Definitely a fitting song for the end boss of such an awesome game.
#5: I Am (Shadow the Hedgehog)
While there are plenty of awesome final boss themes in the Sonic series, none compare to Shadow the Hedgehog's I Am. It's just so insanely metal and perfectly fitting for my favorite hedgehog.
#4: Regalia (Soul Calibur V)
This doesn't play at the end of the Story Mode. Rather it plays on Algol's stage, and when you fight him in the end of Legendary Souls, Quick Battle, and Arcade Mode. It's just as out of place in the soundtrack as Algol is in the cast of characters, but damn, it's awesome!
#3: Darkness of the Unknown (Kingdom Hearts II)
Kingdom Hearts has always had epic boss battles and battle themes, and this song is definitely no exception. An epic song for all but the 1st part of an epic battle.
#2: It Has To Be This Way (Metal Gear Rising: Revengeance)
It's no secret that Metal Gear Rising's soundtrack is fucking hardcore, and the Final Boss theme is no exception. I fits the mood of the fight very well, like you only have this one chance to stop this madman, and the lyrics describe how his plan is just how he thinks things should be. Almost tragic in a sense, but it doesn't detract from the pure epic of this song.
#1: Cantata Mortis and God in Fire (Dissidia 012: Final Fantasy)
Dissidia 012 is probably my favorite game right now. I don't care what anyone says; If you look past the awkward dialogue, nonsensical plot, and at times, horrible acting, it's a pretty great RPG/Fighting game! This song plays during the Final Battle of the secret chapter of Story Mode. The Ominous Latin Chanting is pretty cool on it's own, but the epic metal is what really makes this the best Final Boss Theme ever!
Well, there you have it. If you disagree with any of this list, blow me. HBM, signing out!