Yea, but isn't to say that Naruto is less important without Sasuke either. Even if this had been a story completely centered on Sasuke, it would be just as droll without Naruto, as Naruto would be without Sasuke. Neither character would be half as interesting without the other. We wouldn't appreciate Naruto's nature if he weren't placed into such a contrast against Sasuke's, and vice versa. What makes them both interesting is that they bring out the best (and worst) in one another. They are so different, yet so very alike that they have helped each other to develop very nicely.
If anything, this exposes Kishi complete inability to write a decent story without that kind of rival.