head to head
Rocket League asks more than Half-Life 2, and the gap is reads.

Execution · Pure Mechanics
Landmark FPS built on physics puzzles and tight gunplay.

Execution · Pure Mechanics
Mechanical car-soccer where execution is the ceiling.
Half-Life 2 leans Execution (Pure Mechanics); Rocket League leans Execution (Pure Mechanics).
Rocket League leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
Rocket League
Aerials, flicks, dribbles, pure mechanical ceiling
Rocket League leans clearly harder on reads.
Half-Life 2
Combine AI scripted, non-adaptive.
Rocket League
Rotations and 50-50 reads against humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2
Almost no randomness.
Rocket League
Almost deterministic physics
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Half-Life 2
Linear progression with no builds.
Rocket League
Training routines, rotation theory
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.