Naughty Bear is NOT forgotten. They just released a game for him this last Tuesday. People don't care enough about the character to request him.
Also, Abe is not forgotten, as I have seen him requested numerous times.
That being said, I would love Arc from Arc the Lad, Justin from Grandia, Selvaria from Valkyria Chronicles, or Ghaleon from the Lunar series, in the game. I particularly would like to see Ghaleon, because he was a great villain, and they don't have very many villains in the game.
ONLY CHARACTER I NEED IS THE PRINCE OF PERSIA
prince of Persia moveset: http://community.us.playstation.com/t5/PlayStation-All-Stars-Battle/Prince-of-Persia-in-all-stars/m-p/38273897#M125640
Hmm I would say these forgotten characters should be in. They were AWESOME and most people probably remember them, espescially if they played the PSP a lot.
Soma (Gods Eater Burst)
Minato Arisato (Persona 3 Portable)
Here's a PSX one:
James Sunderland (Silent Hill 2)
Naughty Bear sounded good at first, but it bombed in the end. Oh well it was a good idea. He would just sound weird in this game, I don't know but it kinda makes me laugh a little bit lol. NB was just so crazy if I remember right.
Scaler was actually really awesome, too bad it was overshadowed by Sly Cooper, Jak & Daxter, and Ratchet & Clank during the time of it's release. I would've enjoyed a sequel.
My Mains: Sly Cooper & Sackboy
My Subs: Ratchet & Clank, Sir Daniel, & Parappa