head to head
Neither is simply harder - they are hard in different places. Gothic 3 demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
An open-world action RPG blending clunky combat timing with long-haul character and faction planning.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Gothic 3 leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Gothic 3 leans a little harder on execution, though the gap is small.
Gothic 3
Real-time melee timing and kiting matter.
Portal 2
Portal placement requires some precision but timing is lenient.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Gothic 3
Wildlife and orcs follow fixed AI.
Portal 2
No opponent; puzzles are static.
Gothic 3 leans clearly harder on variance.
Gothic 3
Unknown world content on first run.
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Gothic 3
Learning points, faction routes, and gear progression decide power.
Portal 2
Solving the puzzle's logic IS the entire game.
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.