I think Shadow is also an element in IV, but really outside of Fire, Ice, Lightning, and Holy, the Final Fantasy games doesn't give much prominence to elements. Formahault actually that sounds like a lot for earth given in other games it's showed a lot less love. in Final Fantasy IX the only way to deal earth damage is with Quina's Earth Shake or with Fenrir who isn't that powerful of a summon. You have a few monsters that use it too. For some reason Poison is both a status and an element in VIII. It's been a while since I played VIII so I can't really comment on how important it was, but my mind is telling me it was barely there outside of Bio. I'm not sure how many enemies were weak to it or hit you with it without also inflicting poison.

Wind also gets kicked to the side. In Final Fantasy IX enemies use the Aero and Aera spell, but for some reason Vivi can't cast them. Your only two ways to deal Wind damage is through Quina's Twister and Eiko's Millenial Decay which you might not know even exists for several playthroughs. The wind element also has hardly any summons. It's a secondary attack for Fenrir and I think XII has one, but I think that's it. The game where water probably has the most presence is in Final Fantasy X because elemental attacks are way more emphasized in this game compared to all the others I've played. Nearly all flans can be taken out with a single spell from their elemental weakness and due to the sensor ability that is extremely easy to get you always know when an enemy is weak to a certain element. It's the only one in the series I think that gets three tiers of spells like the fire, ice, and thunder trinity. Oddly, despite this Leviathan isn't in this game. Hey, but the protagonist's signature weapon is a water element weapon.

I think Holy has always been just one spell, a weapon or two, and sometimes a summon in the whole series. While this is similar to other elements I've mentioned I feel it's ok with Holy. The spell is always among the most powerful you'll have and it's even considered as the most powerful VII as being the counterpart to Meteor. Actually, I think this the only case in which the spell is in the game, but not available to the player.

I quite like the elemental spells in the games, but when stuff like the aero situation in IX pops up it annoys me. I'd like to see a little more focus on them, not necessarily on the level of X, but maybe like how IX did it. I always liked how they put the mid tier trinity elemental spells on their own staff.