head to head
Super Smash Bros. Melee asks more than Tom Clancy's Rainbow Six: Vegas, and the gap is reads.

Execution · Competitive PvP
A platform fighter with one of the highest execution ceilings in any competitive game, layered on top of deep human reads.

Execution · Competitive PvP
Tactical gunfights testing aim, entry planning and prediction of human opponents online.
Super Smash Bros. Melee leans Execution (Competitive PvP); Tom Clancy's Rainbow Six: Vegas leans Execution (Competitive PvP).
Super Smash Bros. Melee leans clearly harder on execution.
Super Smash Bros. Melee
Wavedashing, L-cancels, and tech-chasing set an extreme physical ceiling
Tom Clancy's Rainbow Six: Vegas
Aim and snap-to-cover gunplay punish slow hands
Super Smash Bros. Melee leans clearly harder on reads.
Super Smash Bros. Melee
Reading DI choices and opponent adaptive habits is constant and non-convergent
Tom Clancy's Rainbow Six: Vegas
Multiplayer angles and pushes demand reading human opponents
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Super Smash Bros. Melee
Stage hazard RNG and spawn positions add marginal chaos
Tom Clancy's Rainbow Six: Vegas
Terrorist hunt spawns vary modestly between runs
Super Smash Bros. Melee leans a little harder on optimization, though the gap is small.
Super Smash Bros. Melee
Character matchup tiers and optimal movement routing are deeply studied
Tom Clancy's Rainbow Six: Vegas
Room-entry planning and map knowledge are studyable
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.