Dumb question, but has the final fantasy theme being used in all the games? I cant recall hearing it in FF XV or XIII or maybe I was not paying attention (Maybe in XV was the menu music?)
The Final Fantasy main theme at the very least plays in the end credits of every game. In FFXV in particular
it plays at the end during the Royal Edition's final ending scene, remixed as a wedding theme.
Notably, the Final Fantasy main theme has appeared in major moments at the start of various games. The main theme is sometimes called the "bridge song" because of how it plays during the narration and title display when the party first heads out into the world after completing the first adventure in Final Fantasy 1. It was used similarly at the start of Final Fantasy IV, when Cecil departs Baron on his quest. As such, the theme left a strong impression on a lot of people who got into the series in the NES or SNES days.
In general, the main theme is generally used to mark the beginning or the end of the heroes' adventure. Thus, it is often saved for key parts of endings or special opening moments. FFXIV had a great use of the theme in A Realm Reborn, where it plays as your character boards the airship that will take you out of the place where you had your starting levels and into the wider world. Like in FFI and IV, it is used in XIV as a song to mark the hero leaving home and setting out on their hero's journey.
Similarly, the song is used to mark the triumphant celebration of the hero's return. FFV has a great moment where the main theme kicks in at the end of the ending where the credits start to roll. In that scene it celebrates
the resurrection of the heroes who died, if you lost anyone in the final battle.
