The latest Sonic Generations trailer is era-specific, focusing solely on its Sega Genesis level recreations. In the trailer we see the Green Hill Zone (Sonic the Hedgehog), the Chemical Plant Zone (Sonic the Hedgehog 2) and Sky Sanctuary (Sonic & Knuckles).
Watch it here. Sonic Generations is out in November for PlayStation 3 and Xbox 360. A 3DS version will also release.