Sonic Generations

Sonic Generations is a video game that celebrated the 20th anniversary of the Sonic the Hedgehog series in 2011. In North America it was released on November 1, 2011, in Europe it released in November 4, 2011, and in Japan it released on December 8, 2011.

The story of the game revolves around Sonic as he and his classic counterpart race through areas from older Sonic games to free Sonic's friends and restore the worlds back to their original forms all while trying to figure out who brought them to the white limbo and how to get back to their corresponding time periods. Along the way, both classic and modern Sonic face Dr. Eggman in his previous attempts to destroy him.

Course
Green Hill Zone

Chemical Plant (Casino Night in 3DS version)

Sky Sanctuary (Mushroom Hill in 3DS version)

Speed Highway (Emerald Coast in 3DS version)

City Escape (Radical Highway in 3DS version)

Seaside Hill (Water Palace in 3DS version)

Crisis City (Tropical Resort in 3DS version)

Rooftop Run

Planet Wisp

Bosses and Rivals
Metal Sonic 

Shadow the Hedgehog

Silver the Hedgehog

Death Egg Robot (Big Arm in 3DS version)

Perfect Chaos (Biolizard in 3DS version)

Egg Dragoon (Egg Emperor in 3DS version)

Time Eater