I'm very tired of Fairy Tail/One Piece comparisons, which I think are unforgivably lazy. Natsu's personality is actually fairly different from Luffy (he lets his temper control him, Luffy is easy going and fun loving), detractors act as if Lucy is a Nami clone because she's gorgeous (what?!), and One Piece is not the only series that gets to have a zany sense of humor. Does Boa Hancock mean that other manga can't use characters with snakes? Well, we'd better indicte One Piece then, because Naruto got there first with Orochimaru. That's the argument at work there. It isn't a good one.
The influence is unmistakable, but to say that the series is just ripping off One Piece is absolutely ridiculous. If anything lacks depth, it's this pathetically shallow internet meme. FT isn't the best thing out there, but it holRAB its own well enough.