Itachi was able to beat Orochimaru with genjutsu with extreme ease and Orochimaru is not an idiot, so I don't know how Jiraiya who is in the same category as Orochimaru (sannin) is meant to counter it, we have never seen Jiraiya deal with any genjutsu. Also the frog song takes foreeeeever to start, Itachi is not just going to stand around and wait until the frogs start singing LOL only reason that worked with the paths of pein was because Jiraiya was hidden in the tunnel and was being pursued, a well layed out ambush. Even if it was Itachi in that dark tunnel he would not fall for a trick like that anyway. Also you forgot about amaterasu, how on earth is jiraiya going to stop that beast of a technique? By the way a giant frog won't break Susanoo because Itachi has the spirit weapon things, the shield and sword. Oh right and Itachi performed a fatality on Orochimaru during his fight with Sasuke almost forgot that one lol.
