head to head
Neither is simply harder - they are hard in different places. Call of Duty: Modern Warfare 2 demands more variance; Super Street Fighter II Turbo demands more reads.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.

Execution · Competitive PvP
The definitive classic Street Fighter II revision and a founding tournament fighter.
Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP); Super Street Fighter II Turbo leans Execution (Competitive PvP).
Super Street Fighter II Turbo leans a little harder on execution, though the gap is small.
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
Super Street Fighter II Turbo
One-frame links, charge timing, and strict motions
Super Street Fighter II Turbo leans clearly harder on reads.
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
Super Street Fighter II Turbo
Footsies and throw mixups against an adapting human
Call of Duty: Modern Warfare 2 leans clearly harder on variance.
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
Super Street Fighter II Turbo
Minor damage variation; everything else visible
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
Super Street Fighter II Turbo
Matchup knowledge and super meter spend are studied lines
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.