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 console FPS landmark that introduced Master Chief and the ring world.

Execution · Practiced Mastery
Tactical shooter precision built around planned approaches and synchronised takedowns.
Halo: Combat Evolved leans Execution (Practiced Mastery); Tom Clancy's Ghost Recon: Future Soldier leans Execution (Practiced Mastery).
Halo: Combat Evolved leans a little harder on execution, though the gap is small.
Halo: Combat Evolved
Aim, grenade timing, and vehicle control
Tom Clancy's Ghost Recon: Future Soldier
Sync-shot timing and cover gunplay reward precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Combat Evolved
Multiplayer duels reward reading humans
Tom Clancy's Ghost Recon: Future Soldier
Multiplayer flanks involve humans; campaign AI is scripted
Halo: Combat Evolved leans a little harder on variance, though the gap is small.
Halo: Combat Evolved
Covenant AI varies tactics slightly
Tom Clancy's Ghost Recon: Future Soldier
Encounters are designed set pieces
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Combat Evolved
Weapon sandbox knowledge and encounter routing
Tom Clancy's Ghost Recon: Future Soldier
Gunsmith loadouts and approach planning are the tactical layer
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.