head to head
Neither is simply harder - they are hard in different places. DOOM (2016) demands more optimization; Fruit Ninja demands more variance.

Execution · Pure Mechanics
Push-forward arena FPS where movement and aim are the whole game.

Execution · Pure Mechanics
A swipe-em-up arcade game where slicing accuracy against random fruit spawns is the whole skill.
DOOM (2016) leans Execution (Pure Mechanics); Fruit Ninja leans Execution (Pure Mechanics).
DOOM (2016) leans a little harder on execution, though the gap is small.
DOOM (2016)
Aim, movement, glory-kill timing all peak.
Fruit Ninja
Swipe accuracy and combo timing
DOOM (2016) leans a little harder on reads, though the gap is small.
DOOM (2016)
Demons scripted attack patterns.
Fruit Ninja
No opponent
Fruit Ninja leans clearly harder on variance.
DOOM (2016)
Minimal encounter randomness.
Fruit Ninja
Random fruit and bomb spawns
DOOM (2016) leans clearly harder on optimization.
DOOM (2016)
Rune and weapon mod picks meaningful.
Fruit Ninja
Combo and crit systems are shallow but real
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.