head to head
Halo: Combat Evolved Anniversary 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
A sci-fi shooter where aim and weapon-switching against scripted alien enemies is the core test.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Halo: Combat Evolved Anniversary leans Execution (Practiced Mastery).
Halo: Combat Evolved Anniversary leans clearly harder on execution.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Halo: Combat Evolved Anniversary
aim and grenade timing carry combat
Halo: Combat Evolved Anniversary leans clearly harder on reads.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Halo: Combat Evolved Anniversary
covenant AI is scripted, not adaptive
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 Anniversary
enemy spawns and drops vary
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 Anniversary
weapon sandbox and routes are solvable
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.