Ok, I think we need a hefty does of the Brawl poll.

This is the poll Sakurai conducted on the old site (in Japanese only). Take a look

King Dedede(5) - CONFIRMED!
Diddy Kong(4) - CONFIRMED!
Geno(4)
Ike(4) - CONFIRMED!
Ridley(4)
Captain Olimar & Pikmin(3)
Krystal(3)
Takamaru(3)
Windwaker Link(3)
Animal Crossing MC(2)
Claus(2)
Demiru(2)
Isaac(2)
Jeff(2)
Kawasima(2)
King K.Rool(2)
Lip(2)
Lucas(2) - CONFIRMED!
Mega Man(2)
Oguma(2)
Ouendan(2)
Sukapon(2)

As you can see, many of the top characters are playable in Brawl, and look at who is one of the tops. Ridley. He will probably be playable. He can be resized. And the only boss we have is a bit character in the Mario universe. Chances are good he will be playable, but probably hidden.

Ok, I think we need a hefty does of the Brawl poll.

This is the poll Sakurai conducted on the old site (in Japanese only). Take a look

King Dedede(5) - CONFIRMED!
Diddy Kong(4) - CONFIRMED!
Geno(4)
Ike(4) - CONFIRMED!
Ridley(4)
Captain Olimar & Pikmin(3)
Krystal(3)
Takamaru(3)
Windwaker Link(3)
Animal Crossing MC(2)
Claus(2)
Demiru(2)
Isaac(2)
Jeff(2)
Kawasima(2)
King K.Rool(2)
Lip(2)
Lucas(2) - CONFIRMED!
Mega Man(2)
Oguma(2)
Ouendan(2)
Sukapon(2)

As you can see, many of the top characters are playable in Brawl, and look at who is one of the tops. Ridley. He will probably be playable. He can be resized. And the only boss we have is a bit character in the Mario universe. Chances are good he will be playable, but probably hidden.

^But if you look there, all the characters announced (besides PT) were on that poll. Wario and Pit were also popular before Brawl. Popularity means alot.

In fact, look  here

http://nsider2.com/forums/Reference-Guide-Sakurai-s-jou-t3061.html

(Sorry, Anchor not working for me). As you can see, almost all the popular characters made it in as Playable. Marth, Bowser, Peach, Ganondorf, Sheik/Zelda, Mewtwo, Falco even characters like Y. Link made it in. Popularity means the world. Geno probably wont be in due to copyrights, but Ridley is the major villian (or fugure) of the Metroid games. The characters who scored really high are garrenteed playability. 

there were 25 characters in melee right?.... how many for N64?

Well they've confirmed every (4) rated character from that poll other than Ridley and Geno. Square owns Geno. Nintendo owns Ridley. It could happen.

Bacon, I have no idea how I messed up the bullet points. I really just copy-pasted it and they turned into #'s on me. But at least I didn't throw in a thousand Kirbies.

12 characters in the original Super Smash Bros.

8 starters (Mario, Pikachu, Link, Fox, Samus, Yoshi, Kirby, DK), 

and 4 unlockables (Luigi, Jigglypuff, Ness, and Captain Falcon) 

 12. 8 startes, 4 hidden.

Some Ideas for Bosses
- Ridley
- Raquaiza
- Metal Gear Rex / Metal Gear Ray
- Egg Man (Dr. Robotnik)
- King K. Rool
- Andross
- Team Rocket
(and more)

 Fix'd

Not sure why everyone assums he's going to be a boss and not playable. He's got the popularity, expecially in the US. And Metroid needs more reps.