@taboo:
I don't think Luffy is dumb, he's just simple. He understands well enough if something is explained out to him.
That's basically Goku, but by Oda and Luffy's own admission, Luffy himself is stupid.
@AnimeNewtype101:
I don't know about that, I mean if he was truly that stupid then he wouldn't have been able to defeat true geniuses like Kuro and Crocodile. In the fight against Crocodile he figured out that liquids was Crocodile's weakness.
Let's exclude "fighting genius" from discussion, since that tends to apply to all shounen heroes.
@AnimeNewtype101:
I highly doubt that Naruto would have been able to figure that out. He probably would have just used Kage Bunshin and Ransengan over and over.
But Naruto mastered the Kage Bushin no Jutsu, which is an advanced form of his formerly worst jutsu, in the space of thirty minutes.
@AnimeNewtype101:
I mean comparing Luffy to Naruto. Luffy who's able to come up with pratically new uses for his power in every battle, and two new battle modes in a few weeks. Naruto, who after 3 years of traveling with a super-prodigy like Jiraiya is practically the same idiot who knows less than your basic genin and is still using the same two attacks over and over and is only now coming up with a single new attack which will undoubtly get spammed to death.
That's probably Jiraiya's fault, not Naruto's. The fabled Janken comes back to haunt us; Ebisu is a better teacher than Kakashi, Jiraiya is a better teacher than Ebisu, but Kakashi is a better teacher than Jiraiya.