This is difficult. Itachi's Mangekyou techniques are a bit gamebreaking and without them, as in their second fight, it would be a lot closer.
I'm narrowly in Kakashi's camp on this one. Itachi has the edge in genjutsu, Kakashi in ninjutsu, and they're roughly comparable in taijutsu. Intelligence-wise I believe Kakashi is the victor.
One thing which I'm a bit annoyed about is the constant comments about Kakashi "needing Naruto's help" in the fight againt Itachi. He didn't. In the fight, Naruto gets caught in a genjutsu, gets help to escape, and runs forward with a Rasengan to finish off, and this is important, a distracted and immobilized oppnent. Kakashi outsmarted Itachi, and I'm fairly sure he'd have been able to "run up and Rasengan someone" himself.
First fight: Kakashi gets owned due to Tsukuyomi(, which is disabled in this round).
Second fight: Kakashi outwits and eliminates his opponent.
I KNOW ITACHI WAS AT 30% CHAKRA! I KNOW THIS! DON'T TELL ME!
What he wasn't was at 30% brain-capacity.