I think if they were game mechanics
Air:
Air would be related to agility obviously, and maybe stealth, they are faster, jump higher, and maybe have abilities that make them temporarily fly, or they can dash or jump high on a fast speed.
Their damage would most likely area damage, and they may have ability to knockback enemies
Earth:
Earth would be related to defense, they are mostly have single target damage since earth isn't splashy, they have large health.
They may have abilities to create barrier or walls of rock, which correspond with their defensive style, maybe they can also deal melee damage more than other.
Fire:
Fire is obviously the most common power in game mechanics, even if the game isn't about elemental abilities, usually it focus on attack.
I think fire would have area damage and damage overtime, and they are good in area control since they can set some areas in flame to block enemies.
I think out of all, Fire will have the most damage output since it focus on damage, and maybe area control, but lack of defense, maybe except crowd control by stunning enemies with Lightning
They can burn enemies and deal damage overtime which is annoying and could be spread to other enemies
Water:
This one is more like a support, first of all, it can heal, maybe both yourself and teammates, it may also have crowd control since it can freeze enemies or slowdown enemies, and their attack is also area damage, like air and fire, and maybe they don't focus much on damage but they can be painful if they use ice as an attack since it could be sharp. but it's limited
What do you think, do you have any idea? let me know in the comments