I don't want to compare the things Itachi achieve at young age and paired next to his brothers.
Sasuke is a genius nothing more if he was a prodigy Chunin exams should've been a breeze he should've graduated early from academy.
It's level of competition that caused itachi and kakashi to graduate the academy at such a young age as well as progress through the ranks like they did, to prove this look at the shinobi that kakashi had to fight as a kid up until the start of Naruto. He had to fight, asuma who is average, he had to fight kurenai( who is one of the weakest women shinobi ever, gai is the only shinobi that is exceptional from kakashi's generation besides himself. And Itachi's is even worse, his opponents aren't even known at all which means they are were suck fighters. Sasuke grew up fighting the Main, neji( who was the most skilled kid we have ever seen, lee, gaara who would have killed kid itachi or kid kakashi, sauske's had to fight harder competition which is why you think the rankings means something in this case when they don't because sasuke's level of competition > itachi's when they were young.