The only way Halo 4 takes more skill is you have to be proficient with a wider variety of weapons.
With that said, Halo 3 took much more skill overall. As others have pointed out, random ordinance drops and customizable loadouts makes for very random gameplay. The better players will still win the majority of the time, but not as consistently (or by as much of a landslide) as in Halo 3.
In Halo 3, I'd say the truly better player would win 95% of the time. Halo 4 is more like 75%.