Orochimaru kills the third and Kazekage,defeats Naruto 4-Tailed fox mode (I believe Jiraiya took a blow from N4TF and almost died),draws with Jiraiya and people still think Jiraiya was stronger??You are 98% wrong my friend. Orochimaru was indeed a very respected shinobi, but he was not nearly as strong as Jiraiya. Jiraiya could kill both Itachi and Kisame, very strong shinobi. Orochimaru was always frustrated because he never stood a chance against Itachi...Also, I agree that Jiraiya would have had an advantage if he had known about Pain, but I highly doubt he would have been able to beat him. Naruto had information on Pain and was stronger than Jiraiya, and only won due to the fact that Pain was weak at the beginning of the fight and thanks to the aid of the Kiuubi at one point during their fight.
Even Jiraya aknowledges that Orochimaru is as strong as him throught the series.
You are so wrong,Kisame asks why to Itachi saying that he could...Which Itachi responds with "i already used Tsukyomi twice and i was forced to use amaterasu,i need to rest somewhere.."..
Itachi could have defeated Jiraiya alone if he intended too since he mandhandled Orochimaru so quickly and easily. He just didn't wanted to kill,much less one of Konoha greats..
Once again,go read the manga and watch the anime,Pein itself says that Jiraiya most certainly would have beat him if Jiraiya knew about the secret ahead of time...