The best 3D Sonic game in my opinion, the reason I think the controls of this game are better than any 3D Sonic game.
10/10
Graphics: Very good, I don't think a PS2/Xbox/GCN can handle the game's graphics it just looks sweet, Sonic is very detailed, everything looks detailed, when it came out it had the best graphics on the Wii, but It's not better than Super Mario Galaxy's graphics or Corruption.
8/10
Storyline: Basically it just fine, I mean the cutscenes are good, a good way to tell a story, Sonic Heroes had a better storyline, actually a way better one, although the Gameplay is way better in this game and offcourse the graphics are better.
Overall:
Pick it up, do not overlook this Sonic game, I think Gamespot didn't give it a score it deserves, but it's the reviewer's opinion and not mine, I say pick it up, I think you'd find it a bit cheaper right now, but it's worth 60$, although it's short, but it has addicting game play, so you'd always be replaying it.