head to head
Neither is simply harder - they are hard in different places. Alien Shooter: Vengeance demands more execution; Grand Theft Auto V demands more reads.

Execution · Practiced Mastery
A top-down shooter testing aim and crowd control against alien hordes.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Alien Shooter: Vengeance leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Alien Shooter: Vengeance leans clearly harder on execution.
Alien Shooter: Vengeance
Aiming and dodging swarming aliens is the core
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Alien Shooter: Vengeance
Aliens rush mindlessly, no adaptation
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Alien Shooter: Vengeance leans a little harder on variance, though the gap is small.
Alien Shooter: Vengeance
Spawns and drops add modest randomness
Grand Theft Auto V
Some mission and lobby randomness.
Alien Shooter: Vengeance leans a little harder on optimization, though the gap is small.
Alien Shooter: Vengeance
Weapon and stat builds reward planning
Grand Theft Auto V
Heists, money loops, builds learnable.
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.