First comparison: the airship theme from FF7, "The Highwind Takes to the Skies" vs. the "Big Whale" theme from FF4.
Both themes have a lot of cymbal clanging, building snare drum and timpani figures, and fast arpeggiation in the accompaniment. The busy-ness in the accompaniment. They sound heroic/ patriotic, they give the feeling that "the sky's the limit"-- no pun intended.
Here's another I jotted down: Compare FF7's "Hurry Faster" vs FF6 "The Unforgiven."
What comparisons do you think of for the same composer but different games?