head to head
Command & Conquer asks more than Portal 2, and the gap is reads.

Optimization · Pure Optimization
Foundational real-time strategy of harvesting tiberium and out-building your rival.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Command & Conquer leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Command & Conquer leans clearly harder on execution.
Command & Conquer
Click speed and unit micro matter
Portal 2
Portal placement requires some precision but timing is lenient.
Command & Conquer leans clearly harder on reads.
Command & Conquer
Human opponents scout and adapt in skirmish
Portal 2
No opponent; puzzles are static.
Command & Conquer leans clearly harder on variance.
Command & Conquer
Fog of war hides enemy composition
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans a little harder on optimization, though the gap is small.
Command & Conquer
Build orders and tiberium economy dominate
Portal 2
Solving the puzzle's logic IS the entire 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.