I think what made the original character so unique is that it was a random superpower assigned to a totally unrelated animal. Hedgehog + Superspeed, Fox + Flight, Echidna + Superstrength. Then most of their appearence was designed around their power rather than their species, with their animal species being mostly incidental. The only other character who reasonably falls into this pattern of design is Blaze. Nearly every other character since then has been Animal Stereotype = Ability, so they only work on one level instead of two. Er - not counting Shadow and Silver of course, who are just clones of Sonic in terms of appearence and design.So yeah, how exactly DID those fellas in the original Sonic Team pull it off?... Coming up with a character that isn't incredibly generic isn't exactly an easy thing to do, I've found, but regardless it's something I'd like to have done at some point. Bodes well for moving on to more original work than fan characters, I'd think.
I mean, we have a gliding bat, fishing cat, strong alligator, invisible chameleon, flying bee, flying rabbit (using ears to fly is a pretty generic cartoon concept), etc. etc. It'd be like going back in time and making Sonic, Tails, and Knuckles a Cheetah, Bird, and Gorilla, respectively. It'd lose a lot of its quirky charm.