You know damn well that's debatable. Final Fantasy 5 &4 also had some nice music to them. Not all of it was nice, but neither was Final Fantasy IV's. I can agree that in general it did have better, but some songs by Final Fantasy 4 and Final Fantasy 5 were really great. I'll name a few, just for the sake of music.
Final Fantasy 4:
Tower of Bab-li.
The Red Wings.
The Core.
Melody of Lute.
Golbez, Clad in Dark.
Dancing Calobrena.
Illusionary World.
I personally like Dancing Calobrena the best. It's a dark sounding opera music, and it's really awesome to my ears.
Final Fantasy 5:
The Decisive Battle.
The Steam Powered Ship.
Battle with Gilgamesh.
Intension of the Earth.
Prelude of Empty Skies.
As I feel, you feel.
Beyond the Deep Blue Sea.
It's a tough choice, but Prelude to Empty Skies is probably one of the best area musics in any Final Fantasy. It just sounds ''badass'', then evil, it's cool. But to know what I mean you would need to listen to it firsthand.