In light of the recent flailing on Sega's part, promising fan-made projects, and subsequent disagreements among fans regarding how a Sonic game should play, I want to go on the record that Sonic is NOT about going fast!
The original trilogy plus CD and Knuckles were physics-based platformers that rewarded skilled players by allowing you to maintain momentum (speed) if you knew your way around a level. What made them fun to play was the novel experience (at the time) of controlling a pinball-like character with relatively advanced 2D physics that made rolling and bounding along slopes and ramps enjoyable by itself. That's WHY there are slopes, ramps, and loops.
The best decision Sega has made for Sonic was putting fans in charge of Sonic Mania, because they seem to understand what Sonic Team apparently cannot fathom.