It's a post-Adventure 3D Sonic game. Current Metascore: 80.
The final boss. Not only because for the first time in a 3D Sonic game AT ALL, Eggman is the real final boss, but it's pretty awesome in general as well!
The pre-final boss cutscene. Sonic and Tails make it to the orbital elevators only to run into Eggman in the Nega-Wisp Armor. Sonic shoves Tails into the nearest elevator, presses the down button, and sends him back to Earth.Damn.
The game takes on a more light-hearted and comedic tone than the previous Sonic games. When things get serious, however, it gets pretty epic. Sonic manages to pull off a pretty awesome line when confronting the Boss of Asteroid Coaster.
Sonic: You know, I don't like what you're doing to my friends in there. It's messed up, so I'm gonna mess you up!
Eggman using his Badniks as well as all of his modern robots. Seeing a fusion of past and present like that is definitely a CMOA for the doctor.
The DS version has one: At the end of the Asteroid Coaster boss fight, using the Violet Void to finish the boss off results in Void Sonic growing so large that he swallows the entire battleship whole, leaving no trace!
Also from the DS version, granted it could have been hyperbole, but Sonic's response to Omega saying he might surpass light speed at his current rate is downright badass.
Sonic: Light speed? That's small time. There's no challenge!