Jiraiya brought up the most powerful shinobi, clearly, though Hiruzen might be a good competitor in that regard (and Kakashi too).
So...
Jiraiya brought up Pain, Konan, Naruto and Minato.
Hiruzen brought up Jiraiya, Orochimaru and Tsunade.
Kakashi brought up Naruto, Sasuke and Sakura.
I'd say Jiraiya, but in terms of power it was clearly Kakashi. If anything, they all sucked at avoiding their disciples from going all evilz, so it depends on how you want to evaluate them. I'd still say Jiraiya, though.
EDIT: Also, Iruka had little to do with the power of anyone except Naruto. So, I don't believe he's THE best sensei.