I'd say the guy who pulled a meteor from the sky. Actually, two meteors. Had he not been fighting two kage, it would have been a win.
Gaara helped slow it down too, I imagine Oonoki would have died had Gaara not put his effort in because he was looking in critical condition. Madara is scales above most Shinobi. The reason I feel like we don't even need hype is because his presence is the reason that the five Kage plus a battlefield of ninja are getting involved.
All five Kage, the "strongest in the village" are banding together against one guy, and he's holding his own fairly well.
I don't **** ride Madara because I don't know what he can do, but based on the fact that all five Kages felt that they needed to confront him is more than a testament of his strength. The fact that he made Kurama his bitch is more than a testament of his strength. The guy calmly walks up to the Kyuubi and just talks to it like it could understand him at the time. The Kyuubi being the Bijuu that obliterates villages.
I'm more curious about the fight with the Kage and Madara right now than I am about Tobi vs. Kakashi, Gai, and the Jinchuuriki.
However, supposing Kabuto cannot undo the summoning of the Jinchuuriki and they are fully Tobi's due to some sealing he did on them to make them his permanently, then Tobi could usurp his place.
And if Kurama agrees to work with Naruto, then it could be Naruto. The next few chapters will have a band of strongest Shinobi. I'm so excited to see the next coming chapters. I want Sasuke to enter the battlefield.