head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Star Fox 2 demands more execution.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Execution · Practiced Mastery
Dogfighting execution layered over a real-time strategic defense of Corneria.
Grand Theft Auto V leans Execution (Practiced Mastery); Star Fox 2 leans Execution (Practiced Mastery).
Star Fox 2 leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Star Fox 2
Dogfighting and all-range dodging carry every engagement
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Star Fox 2
Star Wolf rivals are scripted aces, not adaptive minds
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Some mission and lobby randomness.
Star Fox 2
The dynamic invasion map shuffles threats per run
Star Fox 2 leans a little harder on optimization, though the gap is small.
Grand Theft Auto V
Heists, money loops, builds learnable.
Star Fox 2
Managing Corneria's defense and intercept priorities is strategic
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.