There are countless of elements that made me fall in love with One Piece but if there is one part that completely seals the deal as a story and an author is Chapter 438/Episode 323. His friends wanted him back, even Zoro. But as a crew, Ussop needed to apologize for his actions, which he did and Zoro was right.
I heard fans saying that "Ussop shouldn't come back, maybe he'll be on a different crew", so he could do the same thing as leaving again to a different crew who wouldn't be as forgiving. I've seen the BS with Naruto with Sasuke, and thats a different can of worms I don't want to disclose on this thread,
The Strawhats will have their silly and crazy adventures, but have sincerity in their actions. Just like Zoro said to Luffy, "Oda may be a crazy crackhead of an author, but he's still the captain of the ship (story)", and I thank God that Oda is writing the story,