Absolutely magnificent! I always had a strong biased preference over Sonic 1/2/CD's sprites, but this? This actually made me love Sonic 3's sprites. He's so expressive, full of charm and is just a joy to look at. From Sonic to Super Sonic, each sprite has been carefully crafted with care for all angles of his actions. Bravo! You've done a fine damn job!
The only thing I can really point out is the shine on his spindashing sprite is on the right, while the shine on his spinning sprites are to the left.
Here's a few suggestions for when V2 comes:
Super Music Selection - via the console, the player could choose what their Super Theme could be: Sonic 3, Sonic & Knuckles, Sonic 3 Proto, Sonic 3D.
End-of-act posing - When S3 Sonic reaches the end of an act, he could pose like he does in Sonic 3 and then have the results screen play out.
I'm eager to see how incredible this mod becomes over time! Keep up the magnificent work! Haha