Sonic is a Gary Stue. He's too OP to the fact that he literally cannot die even though he really should have a long time ago, his homing attack is just button mashing and he has some of the corniest lines ever.
Shadow the hedgehog is a character ruined by sega. Shadow was created to be the ultimate lifeform. He started off as a villain and then reformed to help Sonic save the day. This isn't what makes him great though. The whole reason he was evil in the first place was because he was brainwashed by his creator, Gerald Robotnik. His memory of his be
Metal Sonic is the only badnik to be able to rival sonic properly. He has the same powers if not better and could actually beat Sonic if not for Sega wanting their mascot to always win. He is also independent as seen in Sonic Heroes when he rebelled against Eggman. He doesn't get enough love.
Silver is a victim of 06's terrible story. Given the chance he could be amazing. He is a Sonic with a story of being alone with blaze trying to defend his destroyed home constantly. He isn't a bad character, just the situations in which he was brought into the universe was
Blaze was perhaps the first female mature character in the Sonic games. She doesn't need to be as cute as Amy or Cream, and neither does she need to be a sexy bombshell like Rouge. With strength, courage and the willingness to sacrifice herself, she's become a fan favorite despite being a relatively recent creation.
(Fix) ...and managed to convince Omega and Shadow, despite their initial efforts to destroy each other in their first meeting, to team up with her, forming Sonic Heroes' Team Dark.