head to head
Halo: Combat Evolved asks more than Grand Theft Auto: San Andreas, and the gap is execution.

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

Execution · Practiced Mastery
The console FPS landmark that introduced Master Chief and the ring world.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Halo: Combat Evolved leans Execution (Practiced Mastery).
Halo: Combat Evolved leans clearly harder on execution.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Halo: Combat Evolved
Aim, grenade timing, and vehicle control
Halo: Combat Evolved leans clearly harder on reads.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Halo: Combat Evolved
Multiplayer duels reward reading humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Halo: Combat Evolved
Covenant AI varies tactics slightly
Grand Theft Auto: San Andreas leans a little harder on optimization, though the gap is small.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
Halo: Combat Evolved
Weapon sandbox knowledge and encounter routing
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.