If i have to rank all 15 then:

V-XIV-XII-IX-VI-IV-II-VII-VIII-XIII-X-III-I

I haven't really listened to XI and the sequel games music is kinda meh. So i will fill in the blanks by ranking the expansion soundtracks of XIV.
Heavensward-Stormblood- A realm Reborn.
There we go. now to go into hiding for 2000 years once more. weee hee hee