head to head
Gears of War 2 asks more than Grand Theft Auto V, and the gap is execution.

Execution · Practiced Mastery
The sequel adding Horde mode to the campaign-plus-versus cover shooter formula.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Gears of War 2 leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Gears of War 2 leans clearly harder on execution.
Gears of War 2
Gnasher battles and movement tech set the ceiling
Grand Theft Auto V
Driving and shooting demand decent inputs.
Gears of War 2 leans clearly harder on reads.
Gears of War 2
Human opponents in versus drive prediction play
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 2
Horde spawns add mild randomness
Grand Theft Auto V
Some mission and lobby randomness.
Gears of War 2 leans a little harder on optimization, though the gap is small.
Gears of War 2
Power-weapon timing and positioning are solvable
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.