head to head
Call of Duty: Modern Warfare 2 asks more than FIFA 99, and the gap is execution.

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

Execution · Competitive PvP
Late-90s arcade football execution with couch-versus prediction and bouncy luck.
Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP); FIFA 99 leans Execution (Competitive PvP).
Call of Duty: Modern Warfare 2 leans clearly harder on execution.
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
FIFA 99
Quick passing and shot timing in arcade-leaning football
Call of Duty: Modern Warfare 2 leans clearly harder on reads.
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
FIFA 99
Couch opponents can be conditioned and baited
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
FIFA 99
Era physics produce regular fluke goals
Call of Duty: Modern Warfare 2 leans clearly harder on optimization.
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
FIFA 99
Simple formations and known exploit angles map fast
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.