There are two criteria at play here: first, does it bear the Final Fantasy title, in any form or region? This covers most of what we've got. Second, if the first does not apply, does it feature a major appearance by characters or settings strongly associated with the Final Fantasy series. Kingdom Hearts does, since about half of the major NPCs are from the series. Ehrgeiz does, since it has several playable characters (one of whom is actually on the cover of the game) from Final Fantasy VII. Secret of Evermore might, as well: I was under the impression that the appearances were more along the lines of brief cameos that integral roles, but if someone wants to argue otherwise, I'm listening. Super Mario RPG does not fit under either of these categories: it was never called Final Fantasy: Super Mario RPG (or whatever), and it has but one piece of music to connect it to the series. –