Here's what they need to do:
1. Sega/Sammy needs to stop rushing Sonic Team to get the games done. Let them take their time and get all the bugs out.
2. Go back to having the games be focused on speed. No treasure hunting or shooting stages. All normal enemies should be defeated with just one hit, and you shouldn't have to kill an enemy or stop and break some boxes to get past a certain part of a stage, like you had to in Sonic Heroes. The point of the stages should be just to get to the end, like in the old days.
3. Get rid of the 4Kids voice actors.
4. Stop making new characters. There are already plenty of them.