head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Practiced Mastery
The original 2003 WWII shooter built around cinematic squad set pieces.

Execution · Practiced Mastery
Alternate-history alien-invasion shooter known for its inventive Chimeran arsenal.
Call of Duty leans Execution (Practiced Mastery); Resistance: Fall of Man leans Execution (Practiced Mastery).
Call of Duty leans a little harder on execution, though the gap is small.
Call of Duty
Aim and reaction carry the scripted firefights
Resistance: Fall of Man
Aim and weapon handling against Chimera hordes.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Light multiplayer prediction; campaign AI is scripted
Resistance: Fall of Man
Sizable competitive multiplayer added genuine human opposition.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty
Some spawn and hit unpredictability
Resistance: Fall of Man
Campaign unknowns on first pass.
Call of Duty leans a little harder on optimization, though the gap is small.
Call of Duty
Memorising set pieces and weapon positions
Resistance: Fall of Man
Exotic weapon selection per encounter rewards system knowledge.
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.