>>3 i agree.
changing the name of a character does not make it any more legal. because if everything else is the same except their names, it's still plagiarism. not that fanfiction is stealing - but selling a fanfiction for money and changing a few names to make it legal is simply wrong.
i write fanfiction. i write original works. i publish them online. and would i like to be a professional author? of course. but i don't do it for money, i do it for my own enjoyment.
now let's say the fanfiction didn't follow the original story line (help me stand for example. modern world, no titans, blahblahblah). could changing the name still be acceptable for legal publishing? uhm no. i don't think so.
despite the fact that no - you are not in the same realm - the characters are still the same. you are using their appearances, their personalities. it's like using Emily from the Corpse Bride and renaming her Linda. Names don't make the difference.
So really - unless you have consent from the original authors and their publishing firms (which i highly doubt) - i don't think publishing for money should be an option.
as for the op's original question - definitely.
there are a number of fanfiction that are just as great as the original. in fact - some published authors actually do write fanfiction (marissa meyers is a good example. she, i believe, used to write sailor moon fanfics?). if they were noticed by publishers, they would be selling books like crazy. but alas - that's only 1/100 chance sooo. oh well.