Oh boy, don't even get me started on how the modern games treat the extended cast. They're an accessory at best, and a collectible at worst (both on display in generations)
I understand streamlining the gameplay to Sonic only, but would it kill you to have somebody other than Sonic and Tails actually accomplish something of any worth at all? If you're going to do that, at least just do it like Colours and not bother, it's so clear the only reason they're kept around is to fill out the casts of party games.
Anyway, rant over.