first of all you can't use this to determin your answer, why? because naruto had just return from training he had no idea of what shika was able to do at the time, that was just his memories of shika ability-if your going to use something, use what kakashi "said" when he realise what Shika plan was with they face Hidan, Kakashi is smart and gifted, but once's again without his sharingon, he is nothing-and half of the thing's Kakashi does along with his speed, come's from the sharingon, "hidan could have killed him" as far as sharingon, half of the thing's you see your fav "uchiha" does is not out of being smart, it's because their Keikei genkai is telling the the move's of the enemy before they even throw a punch, it's called "predicting" itachi is smart "yes" we all know this, but when it come's to IQ, no where near Shika. and again itachi vs kakashi- the reason why you thought Itachi was smarter is a miner set back, why? well because Itachi has sharingon in both, eye's and the stamia to mentain it, Kakashi doesn't so when his other plain eye is open it is easy for him to be in gen jutsu, that is why Itachi as always had a top over him, it wasn't really but "Smartness" it's about Pure breed against fake bread. if you are pure of something natrually you have an edge. as for kakashi vs shika ofc kakashi would win, why? well again because his "speed" amd "jutsu" and experiance's of "Nara" ability. (but if Kakashi were to give SHika time to think, it would be check mate for Kakashi. if you think shika think's slow, your just being stupid, why? it's but because he think's slow, it's because he is looking at every aspect of fail vs seccess? which mean's everything that could go wrong in a battle will never happen against him, because he know's. as for Kakashi and itachi well they are diff, they don't do that, they just act on one move and w.e happen's they have to adjust after the siutation fail, if they can. and one of the main reason why they can do this, is again "sharingon "predicting ability" and their experiances in situation's like that. but as for IQ, shika take's it and being smater, because he can also think quickly, and if you wise naruto ppl would of realize there is a reason why he does this now, because when he was chunin and had his first mission to save sasuke, he did not think he just acted amd yes he won his battle but, he failed this mission, that made him "sad" Kishi showed scene's on that(go rewatch it) so he made a promiss to himself never again, which is why he study everything like thousand time's in his head to make sure it goes right. but he can think fast. oh and another thing, someone said he needed ino to cheat in chunin exam, well guess what? "he was too lazy to do it"