I'm not going to say who's on my top 5, but I believe that if you're a jinchuuriki, you're cheating

Jiraya, Minato,former Kage's can easily take the top 5 spot, maybe Itachi, but only because he's smart and planned ahead knowing it will be useful even after he's dead.
I have more respect to Orochimaru than kabuto to be honest.
I bet Oro already collected most of the bodies before he died and Kabuto just tracked down a few afterwards.
experience, pure skills, technique and brain > no experience + power, that's like face rolling a console game on tekken.
Just because a character looks powerful, doesn't mean he's on the top.
and I bet none of you even thought of the 2nd Hokage or the Whitefang, who both have some good and bad reputations on other countries but also very limited information about it.
The thing I like about Naruto is that it doesn't just focus on one chracter, place, event. It includes everyone on the story, even the past events.