Whereas the NES Final Fantasy games were about saving the world, FF4 was about Cecil in particular saving the world. His story is the game's centerpiece, being the one constant character in a constantly changing party, and he thus gets a lot of chances for character growth and development. A brave and moral leader of his country's air force, he starts the game by questioning the ethics of his king's actions, despite him being the father he never had. The entire story is largely about Cecil and other characters trying to redeem themselves for past deeds, leading to some of the most iconic moments in the series, most notably his transition from a Black Knight to a Paladin.

Incidentally, said job change works really well from a gameplay point of view. As a black knight, Cecil is already strong, but has limited growth, casts spells from HP, and can't hurt undead foes. As a Paladin though, Cecil levels up much more quickly and can heal/support his allies.