4. Easily Understandable Magic
If there's one thing that Final Fantasy does well, it's making sense of magic. About to take on a lizard creature?
Chances are that the cold-blooded beast will be weak to cold spells and have some sort of resistance to fire, because that makes sense. Beast has a lot of fur? Then you might want to holster those Blizzaras and bust out a Firaga.
Flying creatures won't be affected by earthquakes, but you can lob some turbulence at them in the form of a wind spell. Simply thinking about the enemy you're facing can usually give players a hint of what sort of spell to cast.
The same applies to the hierarchy of spells in the games. The general rule is that Fire, for example, is the weakest version. A tier above that is Fira, then we have Firaga, and some games go one higher with Firaja. These Ra, Ga, and Ja signifiers are used on most spells to make their power levels easily identifiable to players who are selecting commands in the heat of battle.
It's a simple trick, so effective that it's been used in over seventy (count them) Final Fantasy games.