Sega fans don't know what they want. It seems really hard to me to develop a classic Sonic game in 3d. The whole point of Sonic to me was to run really fast collecting rings going in loops and not getting hit so I won't lose my rings. 3D games are usually less linear and offer lots to do. When the main characters gimmick is run as fast as you can it seems like it's a hard conecpt. I think there was a article about it before.
Mario also does tons of random spin off games, so Sonic can be a knight if he wants to be as well, the execution just wasn't done right.