Sorry, but Itachi was only on there due to Shisui's Sharingan, and it's set to defend Konoha only, and not anything else. Thus, it's useless in any of the fights you'd throw him in. Intelligence is equaled only by Experience, which Nagato has over Itachi. Does it close the intelligence gap? Probably not. But it gets damn close. You are speaking the language of fanboy. Jiraiya's sage mode puts him on a level above Orochimaru, that's my opinion. I respect yours, but I know you're a fanboy. You've yet to explain to me precisely how Itachi would fight Nagato. I've presented you with counter arguments for Nagato, and Tsukiyomi is thrown out. Amaterasu is near ineffective. Susano'o doesn't help much, nor does Totsuka, as he will be too slow to hit him. Ball's in your court bud.