head to head
StarCraft II: Wings of Liberty asks more than Command & Conquer: Red Alert 3, and the gap is execution.

Reads · Grand Arena
Three-faction Cold-War RTS with naval combat where faction asymmetry and multi-front pressure are the core tests.

Execution · Grand Arena
Real-time strategy where hands, reads, and build optimization all matter at the top.
Command & Conquer: Red Alert 3 leans Reads (Grand Arena); StarCraft II: Wings of Liberty leans Execution (Grand Arena).
StarCraft II: Wings of Liberty leans clearly harder on execution.
Command & Conquer: Red Alert 3
Naval and air micro alongside base-building taxes player bandwidth
StarCraft II: Wings of Liberty
APM, macro, micro-control under pressure
StarCraft II: Wings of Liberty leans a little harder on reads, though the gap is small.
Command & Conquer: Red Alert 3
Three-faction asymmetry means opponent choices must be constantly predicted
StarCraft II: Wings of Liberty
1v1 ladder vs adaptive humans modeling you
Command & Conquer: Red Alert 3 leans a little harder on variance, though the gap is small.
Command & Conquer: Red Alert 3
Ore spawning and naval choke variance add moderate uncertainty
StarCraft II: Wings of Liberty
map spawns minor; mostly known
StarCraft II: Wings of Liberty leans clearly harder on optimization.
Command & Conquer: Red Alert 3
Production order and defensive placement are learnable but more flexible
StarCraft II: Wings of Liberty
build orders, economy curves heavily solved
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.