the last traditional sonic game was sonic the hedgehog pocket adventure on the neo geo pocket color.
let that sink in;
the game prior to the advance games was on a 3rd party console and not a sega one.
The sonic advance series was made by dimps; the company that brought us sonic pocket adventure, sonic advance 1-3, sonic rush and even sonic unleashed.
the game goes back to it's roots by just sticking with a two dimensional platformer, and not increasing the speed.
Thanks to this the game seems relatively well