I agree some characters aren't talked about as much because of all the hype for other characters. Some that I think sould be in the game tat aren't talked so much are
Arc the Lad
And Sony Imagesoft characters, Sony Imagesoft was one of Sony's first gaming companies from before PSX, I think they should be more represented it should be more represented in games whether adding them to PSN, cosstumes in LBP, or just putting them in a mascot fighter.
kya is a cool low profile character
prince of Persia moveset: http://community.us.playstation.com/t5/PlayStation-All-Stars-Battle/Prince-of-Persia-in-all-stars/m-p/38273897#M125640
If you want low profile, I have two. I've heard these names a few times.
Jersey Devil - Was a fun and challenging platformer however it didn't sell well due to poor timing.
Blasto - This was the last character to be voiced by THE PHIL HARTMAN.
I was going to include Tomba as well but most people who'vestarted on PS1 or possibly 2 has heard or played his games.
Lowest profile character of them all is Ari and Stan from Okage Shadow King, as it had a small following.