head to head
Neither is simply harder - they are hard in different places. The Elder Scrolls V: Skyrim demands more execution; The Temple of Elemental Evil demands more variance.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.

Optimization · Pure Optimization
Mastering faithful D&D 3.5 rules and party builds against dice-roll swing.
The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization); The Temple of Elemental Evil leans Optimization (Pure Optimization).
The Elder Scrolls V: Skyrim leans clearly harder on execution.
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
The Temple of Elemental Evil
Turn-based clicks - hands never matter
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
The Temple of Elemental Evil
Encounters run on D&D scripts, not adaptation
The Temple of Elemental Evil leans clearly harder on variance.
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
The Temple of Elemental Evil
Dice rolls swing fights until builds overpower them
The Temple of Elemental Evil leans a little harder on optimization, though the gap is small.
The Elder Scrolls V: Skyrim
Skill stacking, enchant loops, and exploits are deeply solvable.
The Temple of Elemental Evil
Mastering 3.5e rules, builds and positioning is the 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.