The Wizardry series is similiar in this way - for example if you are a mage (magic user that specializes in fire and water spells) here are a list of the various fire damaging spells and what they do:
Energy Blast - directed at 1 enemy causing some damage
Fire Ball - directed at a location -causes damage to anything it hits within a certain radius
Fire Storm - directed at a location - causes lasting fire damage to anything it hits within a certain radius - amount of damage goes down each round and lasts from a few to several rounds depending on spell level
Theres also a priest fire spell -
Ring of Fire - creates a ring of fire around the caster which lasts from a few to several rounds depending on spell level - anything next to you during that round is hit with some fire damage - the amount of damage decreases over time (ring moves w/ the caster).
And theres a special Psionic (think telekeneticist) spell:
Psionic Fire - shoots fire from the psionicist in a V like shape outward from the caster causing fire damage to anything it hits in its path
(theres more fire damaging spells in Wizardry but they are similiar to what's already here - like alchemists get "fire bomb" - but it's really just a different name for "fire ball")
Taking a cue from Wizardry you could easily implement the energy blast, keep fire bolt, fire ball, and improved fireball but also add firestorm, psionic fire, and ring of fire.