Actually, most of the coolest songs are by Hamauzu:
Besaid Island
The arrangements to "Song of Prayer"
Blitz-Off
Thunder Plains
Macalania
Crisis
The entire wedding sequence (including my favourite, "Attack")
People of The Far North
Some Day the Dream Will End (!!!!)
Challenge
To the End of the Abyss
Decisive Battle

Nakano spits out the most junk, though some of the songs are pretty good:
Hurry!
Boss Battle
Luca
Welcoming of Maestor Mika
Guadosalam
Summoned Beast Battle

And Uematsu's contributions include "At Zanarkand", "Auron Theme", "Suteki Da Ne", "Seymour Battle", Rikku, Tidus, Yuna Themes, and "Otherworld."

While listening to the FFX OST, I was suprised at the talent of the other composers. I'm sure FF music is going to be left in safe hands after Uematsu's gone (hopefully not for a LOOONG time, he is still the best imo)