But Sonic Unleashed was terrible!
Sonic gameplay was fun, but the decision to put a (playable) Werehog undermined the whole game.
Even though Sonic Unleashed was released in 2008, it started being developed before that. According to a blog, they started working on the engine in 2005, and started developing the game on 2006.
http://blogs.ign.com/SEGA_SonicUnleashed/2008/10/16/A better example of a recent bad Sonic Team game would be Black Knight, but since it's just a spin-off, it doesn't really matter much (in my opinion).
Still, the Sonic Team today is not exactly the same as the one from 4+ years ago, mainly with the merge with SEGA Studios USA and with Iizuka becoming the new head of Sonic Team.
It's possible that they'll be improving from now on, making better games (like Sonic Colors). It's also possible that they'll start screwing up again though....who knows... :<