head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Practiced Mastery
NES platformer that codified boss-weakness ordering and tight jump-and-shoot play.

Execution · Practiced Mastery
Movement execution and route optimisation through a fixed, mappable planet.
Mega Man 2 leans Execution (Practiced Mastery); Super Metroid leans Execution (Practiced Mastery).
Mega Man 2 leans a little harder on execution, though the gap is small.
Mega Man 2
precise jumps and boss dodges under pressure
Super Metroid
Wall-jumps, shinesparks and boss dodges demand precise inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Mega Man 2
robot masters follow strict patterns
Super Metroid
Bosses cycle fixed patterns, never adapting
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mega Man 2
deterministic once stage layouts known
Super Metroid
Item and route knowledge is fixed once discovered
Super Metroid leans a little harder on optimization, though the gap is small.
Mega Man 2
weapon-weakness ordering is the classic solve
Super Metroid
Sequence-breaking route optimisation is the enduring meta-game
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.