The big sellers on steam are usually

Sonic Frontiers
Sonic Adventure 2
Sonic Mania

With Sonic generations periodically breaking the top three. Classic "Pixel" Sonic can sell. Shadow can sell. "Shonen" Sonic can sell. Unfortunately, Sega can't seem to figure any of this shit outside of Shonen Sonic but even then, time will tell if Frontiers 2 goes the way of Superstars in missing the mark.

Sonic Superstars was too expensive BTW.