head to head
Neither is simply harder - they are hard in different places. Castlevania: Lords of Shadow demands more optimization; Grand Theft Auto V demands more reads.

Execution · Practiced Mastery
Cinematic combo-action reboot of Castlevania in the God of War mold.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Castlevania: Lords of Shadow leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Castlevania: Lords of Shadow leans a little harder on execution, though the gap is small.
Castlevania: Lords of Shadow
Combo timing, dodges, and QTE precision
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Castlevania: Lords of Shadow
Bosses and titans are fully scripted
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Castlevania: Lords of Shadow
Deterministic encounters
Grand Theft Auto V
Some mission and lobby randomness.
Castlevania: Lords of Shadow leans clearly harder on optimization.
Castlevania: Lords of Shadow
Combo unlocks and learning fixed movesets
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.