This is actually a fun game... if only Sonic was actually important to the game...
Graphicwise, I think they could have done better. The environments and character portraits are well drawn, but seriously, what happened to the 3D models? Are these people just lazy or do they not know that the DS can handle better 3D graphics? They obviously haven't seen Super Mario 64 DS, Legend of Zelda: Phantom Hourglass, or any of the other good looking 3D games on the DS. BLOCKY IS NOT A REQUIREMENT.
Audiowise, just basic RPG audio stuff, don't need to dwell on it, nothing to really complain about. OK to be honest, I can't rate the audio because I usually play my DS games muted no matter what the music is so it has no part in this review.
The gameplay is where I really start to get upset. You have Sonic and the usual get the chaos emeralds storyline (which is ok, not great for a storyline), but the problem is that you could easily take Sonic out, change the environments a little, and put in completely different characters. There's nothing in the game that is too "Sonic-esque" except for the characters, which (if BioWare wanted) could easily be changed. I am upset with you BioWare, next time give me more. If they put some actual Sonic sort of speed stuff... we can talk then. And it's too easy, half of the enemy attacks miss and you can JUST. KEEP. HEALING YOURSELF.
All in all, it's an ok game, but if you are a Sonic fan, prepare to be upset.