head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Legacy of Kain: Soul Reaver 2 demands more optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
Time-hopping action-adventure where Raziel shifts between material and spectral planes to solve Nosgoth's puzzles.
Grand Theft Auto V leans Execution (Practiced Mastery); Legacy of Kain: Soul Reaver 2 leans Optimization (Practiced Mastery).
Grand Theft Auto V leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Legacy of Kain: Soul Reaver 2
Reaver combat is forgiving; timing helps, never gates
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Legacy of Kain: Soul Reaver 2
Scripted enemies; the story does the surprising
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Grand Theft Auto V
Some mission and lobby randomness.
Legacy of Kain: Soul Reaver 2
Linear structure leaves little hidden beyond plot
Legacy of Kain: Soul Reaver 2 leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Legacy of Kain: Soul Reaver 2
Spectral-material puzzle solving and Reaver upgrades are the test
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.