If anything, perhaps some more well known characters and franchises could have been represented (Toejam and Earl, Streets of Rage, Ecco, Golden Axe etc...) but that is a minor criticism though it could be argued they should be available by DLC, though apparently won't

Love the sonic the hedgehog franchise

If you're going to imitate a well proven franchise like Mario Kart, you should take a cue from Sumo Digital's new combat racer Sonic & Sega All-Stars Racing

All-Stars make up the roster here includes primarily of Sonic franchise characters like Sonic, Tails, Eggman, Amy, as well as characters like Ryo Hazuki (Shenmue)