Heros also don't really need to be smart in some stories. In Hellsing, Alucard is just a badass, he doesn't need to be smart, and in GB, Midou Ban is actually a genius. Kishimoto was influenced by Akira Toriyama (DragonBall), and younger Goku was an idiot, but good at heart, kind've like Naruto. DBZ is probably the easiest to find similarites, but I'm sure there are others you could use.