I dont know why people hate this game i think its good.
The biggest flaw is no doubt the camera angles which suck ass! at one point where u are sonic u are running down a hill then the camera angle move straight away and a big snow boulder comes down the hill after you.
Anyway there are three story modes in this game which all at some point link together.You do these three story modes with sonic,shadow and at the time new character silver.
Predictably the main enemy in sonic story mode is dr.eggman who has kidnapped the princess of soliana and sonic on several occasions saves her but somebody always gets in the way like silver who gets in the way two or three times.
Shadows main enemy is a dark substance called mephiles who takes the shape of shadows body the only diffrence is the the red lines on shadows head are blue on mephiles head.
Silver is in my opinion the worst character he dosent run at high speed he uses telepathic powers which are alright but not as fun.Anyway silver lives in a future which has been destroyed by a fire monster called Iblis and silver is told who the iblis triggrer is and apparently its sonic.After finding this out he goes back in time looking for the "iblis trigger".
Overall i think this is a good game with a few flaws oh yeah and it also has a two-player mode where you can use either sonic,shadow or silver where you can team up of battle each other.This game has very good graphics if you like that.I rate this game. 8.5/10