For Sonic, SEGA are making it more and more like a cashcow. The whole "let's make new ideas" thing is what is making it more unlike what the older Sonic fans are used to. Werewolves, knights and swords, Arabian Night storybook worlds, etc, are just ways of trying to make something repetitive seem new.
Compare Insomniac to SEGA. Resistance or Ratchet & Clank games come out every year and a bit, whereas Sonic games come out two at a time earlier. Like what other people have probably stated, they are rushing the games to get a profit bigger.
Unleashed itself was good, it's just that they could have made it completely "old school" gameplay without the Werehog (as people like JEV3 state, it's a good platformer, but not Sonic), took more time and effort toward it, and made sure it was a single game project at a time.