head to head
Neither is simply harder - they are hard in different places. Endless Space 2 demands more reads; The Elder Scrolls V: Skyrim demands more execution.

Optimization · Pure Optimization
Space 4X with politics and faction-specific economies.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.
Endless Space 2 leans Optimization (Pure Optimization); The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
Endless Space 2
turn-based
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
Endless Space 2 leans clearly harder on reads.
Endless Space 2
AI scripted, some MP
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
Endless Space 2 leans clearly harder on variance.
Endless Space 2
system traits, anomalies
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
Endless Space 2 leans a little harder on optimization, though the gap is small.
Endless Space 2
economy, ships, populations solvable
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.