It does not suck, on the other hand its not great...
GAMEPLAY:
You have to save the princess of soleanna from...have a guess...yes, eggman! You can also unlock shadow and the new-boy, silver, as you go along and then play as them in their own storys. You also play one of the main characters, side hands such as tails. Sonic dosnt run his full speed all the time but sometimes you get to play a part of the level at that speed. This put motion-blur into the game, it seems motion-blur is the in thing for games. There is also a bit of free-roaming and side missions included.
GRAPHICS:
The characters look good and the enviroments also. I dont know what to say about the graphics, yeah there pretty good but look a bit messed up in places, i guess that oblivion does that a bit so its easy to ignore the little faults.
SOUND:
Voices are good, explosions do not sound that good but there not bad. The people around the city do not talk just make a sound or say 'hey' when you talk with them and then the text comes up at the bottom of the screen. Tails gets annoying as his tails spin and make a repetative sound, but thats life.
OVERALL:
Not a bad game, fans of the 2-D sonic will find that this is a big change. If you liked sonic heroes and the games like that you will find this sonic abit slower. Sonic the hedgehog has multiplayer races or co-op on it too. I think this game is good, if you want a game for the younger peoples then this is one of the best youll find for the 360, it can be frustrating at times though.