This game beats both of the adventures!
first the thing that is different from the adventures: instead of controlling one hero at a time, you will be put in control of a team consistiong of three of em. this creates a possibility for great variation in the levels, and not between the levels themselves.
there are 4 teams available, each with his own type of gameplay:
team sonic: this team has levels based on platforming skills
team rose: this is the better for those who are not used to these games and need a tutorial. quite easy and focus on collecting rings
team dark: these guys must handel a ton of enemies.
team chaotix: these new kids on the block will fulfill tasks like 'find this and this'
this is just a quick summary, and all of these teams do the same thing: platforming
how fun is it to play? quite a lot. this is just the level-blasting we like to see from the sonic-games. speeding trough the levels, beeting bad guys and some cool bosses. and altough this game seems easy, you will be able to unlock a superhard mode after getting an all-a rank. nice gameplay we want to see.
the graphics are almost perfect as well. some great cinemathics, and a nice view over the games stages. everything is detailed, and ready to rock.
sound is just fine. some nice tracks, and it fits the world, but its just not amazing.
my overal advice is: buybuybuy! the game is cheap now, and its fun for everyone!