Shika did forfeit because he just wanted to; his skills were already proven any risk he would take would harm him. Shika sometimes took help; but that does not change the fact that he leaded them; also he made a whole stratgy for the team when they were about to attack Kakuzu and Hidan. Itachi's sacrifice is not related to battle intelligence, it does not require to have high intelligence skills to be a sacrificing person.That may be true; but if it was Shikamaru & Kakazu, I think he would've lost.
Also, he would've lost to temari, If he Didnt forfeit, & if he would've took risks like Naruto he might've succeeded with that battle.
More the less, Shikaku did lead them , but with some help.
While on the other hand, Itachi had to do everything himself his whole life.
& when the end came he was willing to sacrifice everything.
Just like batman, his son was killed many of times through out the comic series, also, superman.
But superman, went psycho.
While batman never lost his cool.
He uses most of all his gadgets & still win. & that might've happen with Shikamaru if he Didnt forfeit that match.
Itachi is smart; aswell with some others in the list; but if Hashirama and Tobirama(they are smart; but they are not one of those who has the smarts as their sharp-skill) is there, the Shika-dudes must be too.