head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto: San Andreas demands more optimization; Star Wars: Episode III - Revenge of the Sith demands more reads.

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

Execution · Practiced Mastery
A movie tie-in testing combo timing against scripted duels.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Star Wars: Episode III - Revenge of the Sith leans Execution (Practiced Mastery).
Star Wars: Episode III - Revenge of the Sith leans a little harder on execution, though the gap is small.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Star Wars: Episode III - Revenge of the Sith
Lightsaber combos and blocks need modest timing
Star Wars: Episode III - Revenge of the Sith leans clearly harder on reads.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Star Wars: Episode III - Revenge of the Sith
Versus duel mode adds light human prediction
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
Star Wars: Episode III - Revenge of the Sith
Encounters are fixed movie-scripted setpieces
Grand Theft Auto: San Andreas leans clearly harder on optimization.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
Star Wars: Episode III - Revenge of the Sith
Combo unlocks and boss patterns are quickly mapped
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.
full breakdown
Grand Theft Auto: San Andreas →
full breakdown
Star Wars: Episode III - Revenge of the Sith →