head to head
Sonic Unleashed 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
Sonic alternates breakneck daytime boost stages with brawling night levels as the Werehog.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Sonic Unleashed leans Execution (Practiced Mastery).
Sonic Unleashed leans clearly harder on execution.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Sonic Unleashed
Daytime boost stages demand reaction-speed precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Sonic Unleashed
Scripted enemies in both forms
Grand Theft Auto: San Andreas leans a little harder on variance, though the gap is small.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Sonic Unleashed
First-run stage hazards arrive fast and unseen
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
Sonic Unleashed
S-rank routes and Werehog combat upgrades 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.