Interesting...I'm not really into Sonic right now, but this seems like a neat idea. I have faith, but I'm not going to say for sure if this will be good; I don't share "mainstream" opinions about Sonic, but his recent games have still been hits-and-misses for me, and just because it's 2D isn't a guarantee of quality (Sonic Advance 2 is my least favorite Sonic game of all time, although 1 and 3 were good). The new concept behind the whole thing, though, sounds promising.
Why don't I post my thoughts on each of the six games PaperLuigi posted, to give you an idea of where Sonic stands with me (these are just my opinions)...
Sonic Heroes - I honestly don't like Heroes at all. The "team" gameplay is sort of hard to get a feel for, and the levels are sort of dull and linear.
Shadow the Hedgehog - I've only played two levels of this game, but from what I saw, it seemed like a pretty decent game with some major flaws.
Sonic 2006 - This one's great if you ask me. Fun Sonic Adventure-style gameplay, creative and platforming-heavy stages, and an epic (if rushed) storyline.
Sonic and the Secret Rings - Also great. It had a nice feel to it, and the gameplay with the Wii Remote was fun.
Sonic Unleashed - Meh. The Werehog levels are sort of fun, but the Sonic levels don't really have anything going for them besides "hold button to win". The last three or so are genuinely challenging and fun, though.
Sonic and the Black Knight - It's decent while it lasts, but the game is just too short, and it's not really enjoyable enough to get into it besides completing the main story.
So, Sonic's had his ups and downs as far as I'm concerned. I don't have an opinion on the state of the franchise. I just hope for the best.
Also,