Well the problem I have with elemental spells is that it limits your playing style. For example, if you choose one element, you usually have to stick with it since if you master in all elements, you often end up weaker. Take Diablo II for instance - as a sorceress, like 90% of your skills go to one element, while the other 10% go to others just for protection-based spells. If you were to evenly divide your skills, you would be weak as hell since no one skill would be very strong. This forces you to follow the path of enemies that are weak to your element. If you take on any adventures to enemies that are strongly resistant to your element of choice, the result is a hard challenge with a near-crap reward, making no one want to do it.
Of course, this is a flaw in design and can easily be avoided by not allowing people to master in elements at all (no bonuses or anything towards a specific element), along with keeping spells of different elements at a reasonable relative strength. That doesn't mean you should have Ice, Fire and Lightning that all do the exact same damage, but you could have something like:
- Ice: 10 damage, slows the enemy
- Fire: 12 damage, 50% chance to catch enemy on fire, 20% chance that any enemy they touch catches on fire
- Lightning: 15 damage
Then it becomes strategy. Ice would suck against weak monsters, since the slowing would be useless, but perfect combined with lightning for a big boss. Fire would be great for multiple enemies clustered together because they all catch each other on fire. But after you catch them on fire and/or freeze them (yeah, who said you can't do both?
), you just blast blast blast with lightning. Now you have strategy involved based on who you are fighting, not spamming of a single spell. Then if you want a fast boss that can't be slowed down, making him resistant to ice, so he can't be frozen isn't going to make mages want to quit and start over as a warrior, since how many monsters do you see in games "Resistant to physical attacks"?