Itachi > Jiraiya
Everyone says that the manga says that Itachi says that he and Jiraiya would kill eachother, so he ran away. That means Jiraiya>=Itachi.
That's completely untrue.
Just think a little bit more. What is Itachi's true affiliation? Konoha. What is the the super-powerful Jiraiya a guardian of? Konoha. Itachi would be an idiot if he killed Jiraiya, a guardian of Konoha, so he lied to Kisame about it. Itachi is the 2nd biggest liar of the series.
From what I've seen, Jiraiya has nothing on Itachi. The only thing he can beat Itachi with might be SM, but even then he wouldn't have enough time to enter it.
Amaterasu, Tsukuyomi, Susano'o, Sharingan Genjutsu, etc. From what we've seen, Orochimaru would put up a better fight. And we all know how that went.