Did I say that? I just stated that those spells that tend to make the most damage get used often. Of course it changes with how much power you acquire and how your level adjusts the enemy's toughness.
Consider that it's combat crpg , you get fireball early(relatively early at least), it does an increasing amount of elemental damage(common damage reductions can't hold it back) as you level to a whole lot of creatures and the next similar thing(of course discounting cone of cold, since while it's an area of effect spell, it's not the same) you are going to get is what....sunfire? So, fireball going to see a lot of use. And, if I recall correctly, you can adjust the area of effect in 3.5. No killing party members anymore.
Isn't the most common enemy in crpgs goblinoids anyway? Fireball kills them in droves(exceptions occur of course).
But, I agree with you. There are far more useful spells.