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 · Pure Mechanics
WWII gunfight execution with light multiplayer prediction.

Execution · Competitive PvP
Arcade wrestling that tests reversal timing and little else by design.
Call of Duty 3 leans Execution (Pure Mechanics); WWE 2K Battlegrounds leans Execution (Competitive PvP).
Call of Duty 3 leans a little harder on execution, though the gap is small.
Call of Duty 3
Aimbot trivialises both campaign and multiplayer gunfights
WWE 2K Battlegrounds
Button-mash combos and reversal timing set the pace
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Multiplayer adds modest human positional prediction
WWE 2K Battlegrounds
Human opponents add light reversal mind games
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Scripted setpieces and spawn flow add minor unknowns
WWE 2K Battlegrounds
Power-ups and interactive arenas inject party chaos
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Map knowledge and weapon choice reward light study
WWE 2K Battlegrounds
Shallow systems - move knowledge helps a little
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.