naruto loses to:
hashirama
madara-ems and edo
rinnegan tobi
nagato
Naruto vs. Hashirama = i can only speculte because all we really know about hashi is that he can control tailed beasts, use wood style ninjutsu and he beat madara originally, but did not kill him. anyway my opinion of this hypothetical fight is that hashi wouldn't be able to keep up with narutos speed and the sheer numbers of clones naruto can use to confuse his enemies. so basically naruto would win based simply on hashiramas not being able to keep up with narutos real self.
Naruto vs either Madara = what we are about to see in the manga, basically Naruto gets torn up the first half of the fight and then he comes to the realization that madara is just a sad little boy stuck in a mans body and puts a tailed beast bomb style rasengan threw his chest and BAM! then Madara either A. gets torn to shreds or B. he gets torn to shreds and edo brings him back to be repeatedly torn to shreds by Naruto and eventully runs away to hide...again.
Naruto vs Rinnegan Tobi = mostly a stalemate due to tobi's fleeing factor he won't stand up and fight he cowers from real opponents and uses his pawns to do his dirty work. Once naruto has defeated all his "summoned" dirty tricks tobi will not have anything left I mean he has time contraints on his main jutsu, that kinda makes him a pushover a long drawn out fight could never be in his favor. so my opinion is that Tobi would try some bs way of trying to take narutos power and it would be a sham and naruto would stop him before he finished whatever master plan he managed to come up with.
Naruto vs Nagato = the same basic principal of Narutos actual fight with Nagato/Pain, Naruto hides some clones as backup and tricks Nagato time and time again until nagato coughs up blood and gives up.
I know I didn't go into the specifics of all the jutsu that would be used, but you guys know the jist of my explanations are true. Naruto is a multiplying tank of a character, tricks and jutsus of the like are not going to stop him because he is powerful enough to shatter their illusions and he's just clever enough to trick them into thinking he's done for so he gets the opportunity to slam any kind of rasengan he wants into their face. Not to mention his ability to manifest his chakra into appendages to use in a fight also, he essentially has infinite hands to attack with.
Once again feel free to contest me, I'll lay it on thicker for ya lol and most of the others have been answered quite well by my fellow Naruto supporters so I'll leave the rest as is.
Oh one last thing Naruto vs Orochimaru or Kabutomaru = One hell of an ass whoopin for either of those pale faced Bass turdds. Naruto has increased his power more than ten fold since he last even seen Orochimaru, in my opinion Orochimaru would try to steal Narutos body and then the ninetails would devour Orochimarus soul if he somehow managed it. So IF either of them beat Naruto they would be too susceptible to the hatred caused by the demon and they would essentially be taken over themselves. Besides that nonsense Naruto could never lose to them because they cannot equal his strength any more, they can summon the world if they want to he'd just blow it up trying to get to their throat so he could rip it out because of what they did to Sasuke