I vote Wally West all day! His tenure as Kid Flash showed how heroic and good hearted he was. Then when his mentor sacrificed himself he stood up and took the mantle. He showed how a sidekick is supposed to help a hero until ready to become a hero in their own right. Wally isn’t just the best sidekick, but best comic book character.
I would have to say Robin (Dick Grayson), cause when growing up as a kid, Adam West Batman and Burt Ward Robin always get along well and make a great team.
I’m with Reigan on this one as Dick Grayson Robin will always be the best. Heck, If I recall back in the day Robin was DC best selling book for years.