head to head
Virtua Tennis 4 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
An arcade tennis game rewarding precise timing and reading human opponents.
Half-Life 2 leans Execution (Pure Mechanics); Virtua Tennis 4 leans Execution (Pure Mechanics).
Virtua Tennis 4 leans clearly harder on execution.
Half-Life 2
Gravity gun and shooting demand precision.
Virtua Tennis 4
precise shot timing and positioning
Virtua Tennis 4 leans clearly harder on reads.
Half-Life 2
Combine AI scripted, non-adaptive.
Virtua Tennis 4
human opponents can be out-predicted in rallies
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.
Virtua Tennis 4
minor ball-bounce randomness
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.
Virtua Tennis 4
minimal build depth, mostly play skill
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.