head to head
Rush'n Attack asks more than Half-Life 2, and the gap is execution.

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

Execution · Pure Mechanics
Arcade run-and-stab timing against memorisable enemy spawn patterns.
Half-Life 2 leans Execution (Pure Mechanics); Rush'n Attack leans Execution (Pure Mechanics).
Rush'n Attack leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
Rush'n Attack
Knife-range timing against dense spawns is the entire challenge
Half-Life 2 leans a little harder on reads, though the gap is small.
Half-Life 2
Combine AI scripted, non-adaptive.
Rush'n Attack
Soldiers spawn in fixed patterns
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.
Rush'n Attack
Arcade waves are deterministic once learnt
Rush'n Attack leans a little harder on optimization, though the gap is small.
Half-Life 2
Linear progression with no builds.
Rush'n Attack
Memorising spawn patterns and weapon pickups solves runs
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.