Bert409 said:Metroid still needs a second character(ZSS is not stand-alone), so Ridley still has a big chance to make it in. He's about the same size of SSBB Bowser anyway, so it shouldn't be a problem. Besides, Mother Brain, Kraid, and/or Crocomire would make way cooler boss fights.
I've heard that the hunters from Metroid Prime Hunters may have a shot.
:/ Sylux may be cool.