Judging from the previews, we can at least guess that these characters will represent their series:
- Street Fighter: Ryu, Ken, Guile, Chun-Li and M.Bison
- Breath of Fire (3): Garr, Honey, Momo, Nina, Peco, Rei, Ryu (there's two of them?!) and Teepo
- Ghosts 'n' Goblins: Sir Arthur, Princess Prin Prin and the Red Arremers
- Viewtiful Joe: Sexy Silvia (yes, that's actually her hero-name) and Viewtiful Joe himself
- Okami: Amaterasu (the sun-wolf-god thing) and Issun (the little thing that follows her)
- Monster Hunter: Chaotic Gore Magala (the giant dragon) and Melynx (the cat-thing)
- NiGHTS into Dreams...: NiGHTS and Reala
- Alex Kidd: Stella and Alex Kidd himself
- Billy Hatcher: Rolly Roll, Chick Poacher, Bantam Scrambled (where did they come up with these names?!) and Billy Hatcher himself
- Golden Axe: Tyrius Flare, Ax Battler, Gilius Thunderhead and Death Adder
- Skies of Arcadia: Vyse, Fina, Aika, Drachma, Gilder, Enrique, and Galcian
- Panzer Dragoon: Base Wing (the not-as-big dragon)... and that's it.
Only five of those characters are villains, being Death Adder, M.Bison, Galcian, the Red Arremers, and Reala. I'm curious to see if they're going to be joining Sigma's side for the crossover, or if they might work with Drs. Eggman and Wily for some other nefarious plot.