Although I hate to contribute to the pointless off-topic-ness..
All of the clones are different to the characters they are built around, just Luigi has the most changes. Donkey Kong, for example, is clearly not a clone of Mario, as the two have nothing in common and it is obvious that neither was used as a template for the other. Luigi, on the other hand, is obviously a heavily altered version of Mario. Other clones have modifications made to their move-sets and stats. Young Link is has some big differences between himself and Link, but no-one argues that he isn't a clone.
I think people are just using different definitions of the term 'clone' - some consider any character based on another character a clone, others only apply it to characters which are nearly identical to who they are based upon. No-one is arguing that Luigi isn't drastically different from Mario, just the use of the word. And seeing as it's not an 'official' in-game term no-one can really be considered right.
Anyway, I am glad we seem to have so many characters already, with only two confirmed as unlockable. It seems a little strange to me that Charizard, Squirtle and Ivysaur are usually counted as one whereas Zelda and Sheik and Samus and Zero Suit Samus aren't. The only difference is the stamina stat which Sakurai mentioned (which according to people who played the most recent demo wasn't noticeable, so it might not even be in any more) and the fact that the Pokemon Trainer stands in the background.