head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Wario Land: Super Mario Land 3 demands more optimization.

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

Execution · Practiced Mastery
Greedy platformer where Wario charges through Kitchen Island hoarding coins and treasure.
Grand Theft Auto V leans Execution (Practiced Mastery); Wario Land: Super Mario Land 3 leans Execution (Practiced Mastery).
Wario Land: Super Mario Land 3 leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Wario Land: Super Mario Land 3
Platforming jumps and shoulder-charge timing
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Wario Land: Super Mario Land 3
Entirely scripted single-player levels
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.
Wario Land: Super Mario Land 3
Hidden exits and treasures unknown on first play
Wario Land: Super Mario Land 3 leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Wario Land: Super Mario Land 3
Coin hoarding and treasure routing drive the best ending
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.