Well atleast you're consistent, but barely won, come on. First off all in a fight it doesn't matter whether you barely win or you just demolished the person winning is winning. Everything Naruto did was matched or overpowered by Sasuke. If they had fought without using Sharingan, CS, or Kyuubi, Sasuke still would've won. Even if the two of them are on the exact same level Sasuke would still win.
The very fact that Naruto was being forced to use more and more of the Kyuubi's chakra like that was because he was weaker than Sasuke. Yeah Naruto had his moments where he was using the Kyuubi's chakra to over power Sasuke but those didn't last long and ultimately he still lost. Anyway wasn't this originally about Naruto doing well in combat and the fact is Naruto can't do well in combat unless he has something that gives him a distinct advantage over his opponent. If they are on the same level or even if the opponent's level is just below his he will struggle and he doesn't stand a chance against anyone above him.