Angry Gumball, I know for me it's not exactlly that I heard it in Japanese first that made me not like the dubs, actually there are a number of anime I saw the dubs first, but then I watched the subs, and totally liked the subs better. To me, dubs just don't carry as well as the Japanese ones do. Yeah there might be a *few* exceptions but to me in general, the Japanese voice casts usually fits the characters better and act a whole lot better.
So I don't think that it's exactly that people are biased because they saw the Japanese first, think it's more that the Japanese do a better job. I can point out one example. I watched Fushigi Yuugi dubbed first, and I really didn't have a prob with the dub, I think that's one of the few dubs that I actually don't hate @_@ , but either way, I got the second season on DVD, and watched the subbed version, and totally liked it better.
But on subject, highly highly doubt that a Naurto dub would be any good, same goes for One Piece dub as well, for that matter. Like I stated before, Naruto has such unique character personalities that I think certain voices would match and work well, and most of the time, that's not what happenes in dubs, and in general lacking emotion, on top of that, I would not be surprised if they turned around and made name changes -_- and used some lame stuff like 'art of the doppleganger' for attack names