Tales of Symphonia has some good boss music.
Ultimecias’ boss music, after that lion dude uses Shockwave Puslar. (I forgot his name. ; 
But, of the choices above, I have to go with Atma Weapons’ boss music.
His name is Griever, and the song is titled “The Legendary Beast”. Unless you’re talking about the fight where he uses Great Attractor; that song is called “Maybe I’m a Lion.” And the final boss fight song is titled “The Extreme”.
I don’t know the song names. ; ;
“The Legendary Beast” is the song.
-The Tales of Symphonia music when fighting Remiel and Kratos
-SaGa Frontier
-Legend of Mana
-The boss themes for Janus and Maia in WA3
-The SMRPG boss music (not just the Axel Rangers) was just funny 
The music when you fight Solt and Peppor (in Chrono Cross) is teh bestest evar.
Wait, I change my mind. =o
I like it when you fight Gilgamesh in FFV. Such awesome music… if you know the name of the song, it’d be greatly appreciated.
Out of the choices, I voted for FFIV. But I think Necrosaro’s theme(DQIV) is the best