Its no lie that jiraiya is an extreamly powerful shinobi. Recently I noticed something. He trained Naruto, Minato, and Nagato which, if arent the 3 top shinobi in the narutoverse, then they definitly rank in the top 5. I do understand that students will sometimes surpass their sensei's but that must make Jiraiya one hell of a sensei to train 3 of the strongest shinobi we've seen so far.
Jiraiya was an incredibly powerful shinobi with sage/"hermit" mode and Ma/Pa toad on his shoulders, no doubt. The most dedicated shinobi when it came to teaching it would appear from what we've seen, and with the best results - Naruto, Nagato, and Minato. I mean he gave up three years of his life to train three orphans (Nagato, Yahiko, and Konan) jutsu, so that they could survive on their own (before he knew about the Rinnegan). Who the hell does that? Orochimaru, the kind-hearted soul he was, offered to put them out of there misery, lol, and Tsunade simply wanted to move on, viewing them as a byproduct of war.
Results wise it's actually interesting to compare. Jiraiya's best three students didn't come out of one class like Kakashi or Hiruzen. Hiruzen's three students became the Sannin and Kakashi's three students became Sasuke, Naruto, and Sakura. However, Kakashi's results are confounded because of the other sensei's that Sasuke (Orochimaru + enhancements), Naruto (Jiraiya, Fukasaku [i.e. Pa toad], Killer Bee), and Sakura (Tsunade and Shizune) have had that really defined them post-time-skip. Thus, how much did Kakashi contribute vs. the other teachers? With Sakura, he contributed nothing to her most defining trademark strengths, which are medical ninjutsu and physical strength. With Naruto, he taught him to walk up trees, but Jiraiya taught him to walk on water along with Ebisu, and that formed a basis for sage mode training from Pa toad. Granted, Kakashi invented clone training, which essentially revolutionized Naruto's training and ability to surpass others and learn FRS in a reasonable amount of time as well as shorten sage mode training, which was ingenious. It was also Kakashi who taught Sasuke how to use the Sharingan properly, including how to copy nin, tai, and presumably genjutsu as well as Chidori.
Hiruzen, as far as I can tell, since I know so little about him during this time, didn't suffer from that confound, and thus appears to have trained the Sannin himself, albeit Jiraiya also received training from the toads obviously at some point. Thus, I would put him above Kakashi at 2, albeit I know too little about Hiruzen at this time so it's possible to switch him and Kakashi. As well, whether he was dealt a better class than Jiraiya or not, who knows, but all three of his students excelled at ninjutsu, whereas, we only know of Minato from Jiraiya's toon.
Jiraiya's star pupils all came from different classes and a private tutoring of Naruto who really needed it (He was way behind on the fundamentals [e.g. genjutsu defense], and he the unique issue of learning to control Kurama's power.),
granted Yahiko, Konan, and Nagato could be considered one class and two of which were in Akatsuki while Yahiko died young (precluding judgement). Thus, it's an interesting confound that Jiraiya's best students were spread out, while Kakashi's and Hiruzen's were all in their one class. The confound between Hiruzen and Kakashi is that Kakashi's student's had at least one additional significant teacher for a significant time period (approximately 2.5 years) that shaped their skill set post-time-skip, which I think makes the case for Hiruzen being a better teacher than Kakashi.
Both Kakashi and Hiruzen had the one student who left the village, granted Hiruzen had Orochimaru who turned into a monster with his experiments, but how much can be blamed on Hiruzen, how much was Orochimaru by birth, and how much was Orochimaru's life's circumstances (e.g. the death of his parents, as mentioned by Jiraiya)?
Further, I think Jiraiya was a teacher that transcended the definition of a shinobi teacher. First, he taught guts and the will to never give up no matter what over the gaining of knowledge of ninjutsu or other ninja ways (i.e. nindo's).
As well, his writings and teaching were not simply about how to perform nin, tai, and genjutsu, they were about bring about peace and how to bring about the day when people could truly come to understand one another. To my knowledge no other teacher really discussed this much, nor put much of an onus on their students to carry out such a mission. In large part this was due to his prophecy from the Elder sage toad that drove Jiraiya, but I think that was partly an ignition, which he grew to self-sustain. It was these teachings that shaped the final life decisions of two of Jiraiya's students - Minato and Nagato - and that has put Naruto on the course that he's on currently, which may make possible the "great revolution of the ninja world."
I honestly think that these teachings on the value of peace and their deep insights along with those of guts are invaluable and what make Jiraiya unique. As we've discussed, other teachers have produced excellent students; thus, if Jiraiya, simply did a better job, OK, then he was the best teacher. He was incredibly strong, but as we've seen, there are plenty of strong shinobi out there, and Jiraiya is not alone in that category either.
What defines Jiraiya as unique in his contribution to the ninja world is his philosophical contribution to the beliefs of what defines a ninja's way of life (i.e. guts) and the necessity to seek out a way to rectify the ninja system in order to bring about peace as his destiny, and to prepare (i.e. train) and shape the destiny of some of the most powerful shinobi ever to bring that about. That's his legacy. No one else has that in my opinion.
Peace
nah, hiruzen = better teacher oh, and SO6P too is better teacher than he is/was
Hiruzen may have done more with his class of three, but what did he teach them besides nin, tai, and genjutsu? Jiraiya was more than that. The threshold for the Rikudou Sennin was set incredibly low, and we have almost no knowledge as to what he actually taught people vs. what fundamentals he layed out and left for self-discovery. It seems like he was quite busy with his own projects as well (Juubi, two sons, etc.). We don't know enough, so it's not really feasible to throw his name out there. At least that's my thought, but that's just me. I don't see him having years to sit down and work with people hands on teaching them everything like they do these days; rather, more of a philosophy being handed out, with a lot of self-discovery and some hands on perhaps. :shrug:
Peace
He is probably the best sensei in the world, training three potential world changing Shinobi.
Second would be Kakashi.
Kakashi is confounded by the fact that so many other shinobi have trained his students that it makes it difficult to distinguish between his contributions and those of the other teachers like the Sannin, etc. For me, that makes him third with Hiruzen ahead of him. Albeit, I know little about Hiruzen at that time period, so it's not clear that this would hold, so 2/3?
Peace