Sonic Generations (lost game demo; 2010)
Sonic Generations is a game made by Sega to commemorate the 20th Aniversary of Sonic the Hedgehog. It has gone through several versions and codenames during development, such as an early demo version named Sonic Boom (not to be confused with the much-more negatively recieved series of games of the same name) and the early codename of Sonic Anniversary.
Whilst in development, there were several demos, such as the aforementioned Sonic Boom demo, only ever appearing at 2011's E3 Expo. More demos include the first level from the finished game being playable on PlayStation Portable, Xbox 360 (only for Gold Members) and PlayStation 3. However, a demo version of the game that never saw a home release but only available in select stores such as Gamestop and Walmart.
The game consisted of only Green Hill Zone in a Sonic 4 style. It was the same level for the classic Genesis ported into a Sonic 4 format but was only available in stores for a limited time. It is unknown if it was a disc that was put into the consoles or if it was a special version that was loaded onto the consoles. Alas, it shall remain a mystery.
- Shadow the Hedgehog (lost build of unreleased Teen rated version of platformer; 2005)
- Sister Sonic (lost build of cancelled "Sonic the Hedgehog" localization of "Popful Mail" Sega CD side-scrolling platformer; 1993)
- Sonic 3D Blast (found cassette demo tape of unused game soundtrack; 1996)
- Sonic Adventure New Year's DLC (found "Sonic the Hedgehog" holiday-themed DLC; 1998)
- Sonic at the Olympic Winter Games (found iOS game; 2010)
- Sonic DS (lost Nintendo DS tech demo; 2004)
- Sonic Jr. (lost build of unreleased Sega Pico game; existence unconfirmed; 1994)
- Sonic Saturn (lost build of cancelled Sega Saturn prototype of platformer; mid-1990s)
- Sonic Sports (lost build of cancelled Sega 32X sports game; 1995)
- Sonic Synergy (lost original build of "Sonic Boom: Rise of Lyric" Wii U action-adventure game; 2007-2013)
- Sonic the Hedgehog "2006" (lost complete build of Xbox 360/PlayStation 3 platformer; 2006)
- Sonic the Hedgehog (lost build of cancelled Amiga port of Sega Genesis platformer; 1992)
- Sonic The Hedgehog (lost build of cancelled Sega CD port of Sega Genesis platformer; 1992)
- Sonic the Hedgehog (lost Tokyo Toy Show prototype build of Sega Genesis/Mega Drive platformer; 1990)
- Sonic the Hedgehog (lost Winter Consumer Electronics Show 1991 demo build of Sega Genesis/Mega Drive platformer; 1991)
- Sonic The Hedgehog 3 & Knuckles (lost build of cancelled iOS port of Sega Genesis platformers; 2014)
- Sonic The Hedgehog: Awakening (lost build of cancelled "Sonic the Hedgehog" game; existence unconfirmed; late 2000s)
- Sonic X-Treme (found build of unreleased Sega Saturn video game; 1996)
- Sonic-16 (lost build of unreleased Sega Genesis/Mega Drive game based on "Sonic the Hedgehog" animated TV series; 1993)