First party: Sir Daniel Fortesque (MediEvil), Wander (Shadow of the Colossus), Sackboy, Ratchet & Clank, Nariko (Heavenly Sword), Spike or Specter (Ape Escape), Kat (Gravity Rush), Lammy (UmJammer Lammy), Vibri (Vib-Ribbon), Rudy Roughnight (Wild Arms), Ari & Stan (Okage), Emmet Graves (StarHawk), Gabe Logan (Syphon Filter), Garl Vinland (Demon's Souls), Jennifer Tate (Primal), Captain Blasto, Rau Utu (The Mark of Kri), Dart (The Legend of Dragoon), Ellen or Keats (Folklore), Toan (Dark Cloud), Jeanne d'Arc, Max or Monica (Dark Cloud 2), Robbit (Jumping Flash), Tomba and Alundra.
Third party: Crash Bandicoot (PS1 era), Spyro (PS1 era), Snake or Big Boss (Metal Gear Solid), Gex, Rayman, Ty the Tasmanian Tiger, Musashi (Brave Fencer Musashi), KOS-MOS (Xenosaga), Sergeant Cortez (TimeSplitters: Future Perfect), Jutah Fate (Silent Bomber), Klonoa, Gene (God Hand), Alicia or Selvaria (Valkyria Chronicles), Lenneth (Valkyrie Profile), Kazuma Kiryu (Yakuza), Hero Prinny, Gitaroo Man, Abe (Oddworld: Abe's Oddysee), Crypto (Destroy All Humans!), Croc and Raziel or Kain (Legacy of Kain).
They could fill the whole roster with first party characters alone.
I personally don't care much about the cast of this game too much as long as they are interesting and unique... But from a characters that I like stand point I'd like to see sackboy, ratchet and clank, wander, ico, snake, cloud, nightmare, prinny and max (dark cloud 2)
None of these are make or break though. I would be a tad dissapointed to not see sackboy but cmon really
Oh and I would also be very delighted to see a colossi from shadow of the colossus appear as a stage. Picture fighting on the back of a huge beast.... that would be so siiiiick
Ratchet and Clank
The franchises that need representation in some form, be it characters, stages, and whatnot are:
ICO/Shadow of the Collosus
Everything else is an awesome added bonus