head to head
Diablo III asks more than Fallout 2, and the gap is execution.

Optimization · Pure Optimization
A pure loot-and-build treadmill where set-bonus optimisation and Rift pushing define performance.

Optimization · Pure Optimization
A post-nuclear RPG expanded in scope where tagged builds and Gifted-trait optimization dominate.
Diablo III leans Optimization (Pure Optimization); Fallout 2 leans Optimization (Pure Optimization).
Diablo III leans clearly harder on execution.
Diablo III
Greater Rift pushing has minor mechanical demand in builds
Fallout 2
Turn-based AP system makes twitch entirely irrelevant
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
No meaningful adaptive opponent; co-op is cooperative
Fallout 2
All tribal and Enclave enemies run fixed scripted combat routines
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
Primal Ancient drops and set dungeon RNG drive the grind
Fallout 2
Hidden special encounters and timed events create significant unknown-information space
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
Set bonuses and paragon levelling are almost entirely solvable
Fallout 2
SPECIAL and skill tagging with Gifted trait produce well-known dominant build strategies
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.