Right now I'm listening to the FF4 version of Prologue, and I must say it's damn touching.
There's something about the melody that just - hypnotizes me, and it almost brings tears to my eyes.
It's so simple, yet so incredibly melodic.
And when it's played during the preparation for the final battle, it DOES bring tears to my eyes.

In my opinion, this melody blows everything else into the water; it defines the whole FF series so perfectly.

Laa, laa, laa, laa, LAAAA, laa, laa, laa, la-la-laa, laa, laaaa, laaaa...