[Faceman]

Well obviously anything that allows a negating saving throw is useless when you come up against harder enemies.

So the only attacking spells which are wise picks are Magic Missile (no saving throw, up to 25 dmg) and Burning Hands (saving throw halves, up to 23dmg/2)
Chromatic Orb can do wondrous things at higher levels but only if the traget doesn't save and IIRC it doesn't petrify but only stun enemies at higher level.
Larlochs Minor Drain is a guaranteed hit but not very strong. However it is perfect to interrupt a spellcaster or finish an opponent who was reduced to 1hp by other means (e.g. "Harm")

Some of the defense and other enchantment spells like "Friends" or "Protection from Evil" are useful throughout the whole game.

The main problem with high level enemies however is their magic resistance which will often negate your spells. This is another advantage of magic Missile which checks for resistance with every hit. So your chances of bypassing the Resistance with one of the missiles are quite nice.