Someone found Roy, Mewtwo, Dr. Mario and Pichu fun.
But 3 of those 4 characters were actual clones. Boring or not, those characters had nothing truly unique to them. And Mewtwo was cut because of Sonic - he was planned to be in Brawl until the very last minute.
Every fighting game franchise has cuts. There is probably not a single fighting game franchise that has 3 or more entries that didn't at least cut one character. It's natural. The reality is there can only be so many characters, and adding old ones due to obligation stymies the possibilities of the new roster. Obviously a huge appeal of Smash is the Nintendo aesthetic, and people want to see as many Nintendo properties represented as possible, or new characters from already represented series. FALCO MUST DIE SO RIDLEY MAY LIVE.
But Nintendo's properties consist of more than just Mario and Zelda and Metroid. That's the whole point of the game - to show other stuff from Nintendo's past and present. Of course there's gonna be cuts in some shape or form, but there's a few significant differences between Smash and other fighting games.
For one, hardly any fighting game series is as popular as the Smash Bros. series. The only better-selling franchise of fighting games - as far as I recall at least - is Street Fighter, a series that is a decade older than Smash, has significantly more installments (between the different versions in particular - the SF4 franchise is bigger than Smash currently is), and founded the fighting game genre as we know it.
Edit: Just looked up, apparently Mortal Kombat and Tekken also sold more than Smash, but hey, those series are also older than Smash. Point still stands - Smash is really damn popular.
Second, as you say it, it's Nintendo franchises/characters. There's a lot of people who like those characters, and I'd argue a lot more people are fans of Falco, R.O.B. or the Ice Climbers than there are fans of Rose, Yun or Dudley.
It's just one criteria in an ever-changing list. R.O.B. and G&W are in Smash Bros, not only because of their importance in Nintendo's history, but also because they bring something new to the table that's never been done before, and the same could be said of any of the newcomers this time around. Luigi's no different. He has his own persona outside of being Mario's brother.
I never was arguing Luigi's importance to Nintendo, or his importance to his series, or having his own persona.
You are completely missing my point. My point is that people cry for cutting Wolf because he is a clone, but he shares less moves with Fox than Luigi does with Mario, yet nobody cries for Luigi getting cut due to being a clone.
As a matter of fact, the term "luigified clone" has been coined, while Luigi remains one of the characters closest to his source material.
Hopefully smash 4 is much better. That, and these things can also be patched. Really hope the 3DS acts as a 'beta test' for the Wii U one. 
