head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto: San Andreas demands more variance; Mega Man 5 demands more execution.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.

Execution · Practiced Mastery
Pattern memorisation and precise platforming with a solvable boss-order route.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Mega Man 5 leans Execution (Practiced Mastery).
Mega Man 5 leans clearly harder on execution.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Mega Man 5
Precise jumps and buster timing through gauntlet stages
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Mega Man 5
Robot Masters cycle fixed attack patterns
Grand Theft Auto: San Andreas leans clearly harder on variance.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Mega Man 5
Every stage and boss is identical each attempt
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
Mega Man 5
Weapon-order routing and pattern memorisation solve the 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.