For Critical hits, the PHB states
When you score a critical hit, you get to roll extra dice for the attack's damage...
for acid splash
... A target must succeed on a Dexterity saving throw...
Unconscious (leaving out first 2 bullet points)
- The creatures automatically fails Strength and Dexterity saving throws.
- Attack rolls against the creature have advantage.
- Any attack that hits the creature is a critical hit if the attacker is within 5 feet of the creature.
So a sorcerer sneaks up to a sleeping creature (within 5') with the intention of doing as much damage as possible, and can either firebolt it or acid splash it.
Firebolt — The advantage of being unconscious is negated by the disadvantage of making a ranged spell attack at 5'. If it hits, it is rolled as a critical
Acid Splash — The advantage of being unconscious is now obsolete because the target automatically fails dexterity based saving throws. The spell automatically hits as a critical.
Does the acid splash work this way?