People usually want 9/10 games if they dont have alot of time to play games.
If someone is a fan of a series a 7 or 8 it is ok (like Disgaea, Naruto, sonic, etc) people will pick it up.
The sonic brand sells units. Look at Mario and Sonic at the olymics, its not a very hardcore game, but it sells like crazy cause of the characters!
I enjoyed sonic rush for the DS, but never a 3d sonic. :(