head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

Optimization · Pure Optimization
A classic point-and-click adventure that's a fixed set of logic puzzles to solve.

Optimization · Pure Optimization
A cerebral puzzle-adventure that is essentially a logic puzzle to be fully solved.
Monkey Island 2 Special Edition: LeChuck's Revenge leans Optimization (Pure Optimization); Riven: The Sequel to Myst leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Monkey Island 2 Special Edition: LeChuck's Revenge
no reflex demand, point-and-click only
Riven: The Sequel to Myst
no reflex or physical skill required
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Monkey Island 2 Special Edition: LeChuck's Revenge
no opposing agent to out-think
Riven: The Sequel to Myst
no opponent present in the game
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Monkey Island 2 Special Edition: LeChuck's Revenge
deterministic puzzle solutions
Riven: The Sequel to Myst
fully deterministic puzzle world
Riven: The Sequel to Myst leans a little harder on optimization, though the gap is small.
Monkey Island 2 Special Edition: LeChuck's Revenge
inventory logic puzzles fully solvable
Riven: The Sequel to Myst
pure logic-puzzle solving, walkthrough-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.
full breakdown
Monkey Island 2 Special Edition: LeChuck's Revenge →
full breakdown
Riven: The Sequel to Myst →