Sheik IS Zelda though, which is how she got in. I think one of the qualifications is that each character has to be in at least 2 Nintendo games in order for them to get into the roster.
Sheik got in as you said, since He is Zelda and the fact being is that he was an unused Model left over from Twilight Princess.
If Nintendo put people into SSB who were in at-least 2 games then there's be an awfully large arrangement of characters.
Majora is some ridiculously powerful being that has no real place in a game like Smash Bros.
No because in Melee Sheik and Ganondorf were in thereSheik IS Zelda though, which is how she got in. I think one of the qualifications is that each character has to be in at least 2 Nintendo games in order for them to get into the roster.