head to head
Gears of War 2 asks more than Red Dead Redemption 2, and the gap is reads.

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

Execution · Practiced Mastery
A cinematic open-world western leaning on shooting feel and atmosphere.
Gears of War 2 leans Execution (Practiced Mastery); Red Dead Redemption 2 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
Red Dead Redemption 2
Gunplay and Dead Eye reward aim and timing.
Gears of War 2 leans clearly harder on reads.
Gears of War 2
Human opponents in versus drive prediction play
Red Dead Redemption 2
Enemies use scripted AI patterns, not adaptation.
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
Red Dead Redemption 2
Some hunting and weather randomness, lightly hidden.
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
Red Dead Redemption 2
Loadouts and routes solvable but loose.
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.