Spells for different casting classes (except Warlock whose spellcasting system is different) are *roughly* equal in power. Otherwise, different casters would have different # of slots per day. So yes it is fair to compare spells from different classes.
Alternatively, here are other 1st level single-target damaging spells also on the sorcerer spell list:
-Catapult deals 3d8 bludgeoning but has a larger range (60+90 ft) and is a Dex ST instead of an attack roll
-Chaos Bolt does 2d8+1d6 of a random damage type but has a 1/8 chance of arcing to additional targets
-Ray of Sickness does 2d8 poison damage and can Poison a target
All of these seem comparable to Chromatic Orb's 3d8 damage of your choice in damage type.
Also, it makes absolutely no sense to compare a single-target spell's damage to the damage that an AoE spell would do to a single target; obviously you should assume that the AoE spell will hit multiple creatures (otherwise you wouldn't cast the AoE spell).
