Well I liked the game pretty much but I wouldn't say it would be better than Unleashed. If I was rating it, I'd give it mainly a 7.
1st: Multiplayer kinda sucks. Since there is no co-op mode for the story, no racing on levels, or getting the most score or rings, or finding certain items in a level. All there is, is Last Man Standing which you fight your friend to the end with life, defeat the most solider-ones, work together to beat the giant-one. And hey there's a list of Sonic Games that had decent multiplayer, why not this one?
SonicAdv, 2, and 3 all had multiplayer options. SA2B also did. Sonic Heroes also had decent.
2nd: The level layouts are pretty nice, graphics are just as or a little better than SSR.
3rd: Moves are straightforward, easy to learn.
4th: It is as long as you want to make it. It is only as short as you want to make it. People who rush through games say it is too short, but when you have people that take their time and actually try to enjoy it like me, it is longer.