The best Naruto character is Sasuke, period. He's 10 times more interesting than Naruto can ever hope to be. It's actually pathetic really, that a main character of a shonen is so upstaged by his rival in practically everything in this manga. Sasuke is the better ninja, is smarter, talented, has a more detailed and interesting past, is more dynamic as a character, has the greatest raw potential out of anyone not factoring any power-ups/demons, not as annoying or retarded as Naruto, and is generally better all around.
Naruto on the other hand is a complete idiot, a loser, clumsy, loud, obnoxious, has an inferiority complex the size of a mountain whenever anyone comes and upstages him, has the same personality throughout the whole series which makes him probably the most boring character in the manga (next to someone who doesn't matter like Tenten), and a sorry excuse for a ninja even with Kyuubi. In fact he's worthless without Kyuubi unlike a true hardworking loser like Lee who's actually talented. He fails at being a main character. Characters like Ranma, Ichigo, etc completely blow him out of the water in that respect. The only shonen main character that Naruto is definitely better than is Goku, and that's not saying much as Goku is a freakin boring moron as well.
Even if somehow Naruto became the strongest ninja when he grows up, it's clear that it'll all be due to having a demon in him as we can clearly see how pathetic he is without it. And it'll be due to Kishimoto doing the biggest plot manipulation ever as well.
It's also pretty evident as well that Naruto by himself isn't really that interesting as most people are looking for other characters to inject excitement back into the series after Sasuke left (like people like Kabuto, Orochimaru,
). It's even more evident when everyone is looking for Sasuke's return to bring the manga back on track (as Naruto has no way of doing it with just his character). That's why:
Honestly Kishimoto should have just made Sasuke the main character as Sasuke is his favorite character and Naruto just utterly fails at being compelling. Sasuke is more interesting and more compelling a character than Naruto in terms of backstory, growth+conflict, character design, goals, and just in general. It's interesting that the only times when the manga is at its best is when Sasuke is there or it's about something to do with Sasuke. Go figure.