While Samus and Ridley may have been at similar sizes in the
original Metroid, Smash Bros is based off of the latest appearances of characters (for the most part). All of the Smash Bros characters are based off of their latest appearances in games
outside of Smash Bros. While all Smash Bros character models are
based off of their latest appearances, they are not complete replicas
per se. For instance:
- The Mario, DK, Yoshi, and Wario characters are all original models based off of their latest appearances, with Bowser and DK taking on a much more grimacing look, Peach taking on a frilled, ornate dress, etc etc.
- The Zelda characters are based off of the latest Zelda games - the realistic (Twilight Princess) realm, and the toon (Wind Waker) realm.
- Samus is based off of her latest rendition for the most part, including ZSS, who doesn't look exactly as she did in the Metroid Prime series (well, her head that is), and Ice Climbers, Pit, and ROB being modernized updates to their 20 year old sprites.
- The Kirby characters have been represented three-dimensionally in only two games, besides the Smash Bros series (correct me if I'm wrong), so their appearances haven't changed much at all; and as for Olimar, he has changed minutely from his appearance in Pikmin 1&2.
- The Star Fox characters are completely new renditions, taking inspiration from their latest titles, but revamping them for Brawl, and the same goes for Captain Falcon, who appears like never before.
- The Pokemon characters have never really changed much, as there has been no real mean to do so, however, they've not been presented so well in 3D before Smash Bros either.
- The Fire Emblem characters and the Mother/Earthbound characters resemble their out-of-smash appearances, but Marth has been incredibly updated, along with Ness and Lucas - who remember, have never appeared in 3D until Smash Bros; leaving Ike for last, he too even looks different from his latest FE appearance.
- As for the last roster column, G&W doesn't have much to work with, but Snake and Sonic, being guest characters, are based off of their most famous designs (albeit latest, sans Old Snake).
So, my point? Please take into consideration what a character appears like in their latest rendition
outside of Smash Bros, as that will have a strong effect on their appearance
within Smash Bros. Ridley was included twice as a boss, very large both times, but smaller than his rendition in the Metroid Prime series - why? Because they had to size him down so that he would work with the Smash Bros characters
in the best way possible. You'd have to size him down a little more than half of his Brawl size for playability, and that's not doing such a great character any justice.
Of course Ridley could be playable, I do not debate that. Hell, you could make Godzilla playable if you sized him down, and while that is more of an extreme, doesn't that seem incredibly ridiculous? No one would rightfully want that, and the same goes for Ridley in terms of ridiculing the character.
Thank you for your time,
Spire