Ooo
As someone who spent his early childhood playing Sonic 3 & Knuckles over and over again, I've gotta say, this is very good. You've definitely captured the way we thought about Super Sonic, Super Knuckles and Hyper Tails - growing up as we did surrounded by Dragon Ball Z and Tekken games.
I very much like the clothes, particularly the flared black trousers on Knuckles and Tails. The pencil drawn and shaded artistic style you've employed suits these characters very well. You've remembered all the key defining features of the characters, from Knuckle's white necklace to Tails' fringe to their traditional footwear. And no Sonic Adventure green/purple/blue irises in the eyes either. Kudos.
I notice you opted out of including Tails' Flickies. Good call.