head to head
Neither is simply harder - they are hard in different places. Pokémon Ultra Moon demands more reads; The Elder Scrolls V: Skyrim demands more execution.

Optimization · Pure Optimization
Turn-based team-building optimization with collection RNG and optional human battles.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Pokémon Ultra Moon leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
Pokémon Ultra Moon
Turn-based menus require no dexterity
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
Pokémon Ultra Moon leans clearly harder on reads.
Pokémon Ultra Moon
Only human link battles involve predicting switches
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
Pokémon Ultra Moon leans clearly harder on variance.
Pokémon Ultra Moon
Wild encounters, IVs and catch rolls add randomness
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Pokémon Ultra Moon leans a little harder on optimization, though the gap is small.
Pokémon Ultra Moon
Type matchups and team building are the solvable core
The Elder Scrolls V: Skyrim
Skill stacking, enchant loops, and exploits are deeply solvable.
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.