No one is even considering the original shinobi? I mean Hagoromo Ōtsutsuki himself is technically the strongest one in their world, that is if you don't count in his mother but she wasn't a ninja... She just happened to help bring Chakra into the future generations by "eating" a fruit from the tree...
And if you require it to be someone living in the "current" era then I'd have to say it's Sasuke... Mainly because of his heritage though, I mean if the series would've built more onto his story it would be more clear to everyone that Sasuke have the potential to surpass Madara quite heavily even without the help from Hagoromo.
There's too much to factor in between everyone in the Naruto world to even make a precise answer about this because everyone has dumb luck in pretty much all their battles. If you went by pure numbers you'd have to take a look at Orochimaru who has "mastered every possible technique in existance" or so they say...