Super Smash Bros. Wii-U/3DS Thread of JAPAN TIME!

[Vipershark]

That's because the ONLY relevant character in the entire metroid series is samus, as far as smash bros goes.
People argue about Ridley but somehow forget that he's a GIGANTIC MECHA DRAGON and not fit for a fighting game at all outside of an NPC boss character.
Saying you want Ridley is like saying you want Kraid for an unlockable. It just doesn't work.

Couldn't you make the same argument about Bowser?

No. Bowser is maybe twice mario's size, but if I'm remembering correctly, Ridley is about three or four times Samus' size, and Samus is almost as tall as Bowser.

Ridley is just too big.