Sonic the Hedgehog 2 (October 16th, 1992) for Master System and Game Gear.Re-released in 2008 for Wii Virtual Console and in 2013 for 3DS Virtual Console. Sonic the Hedgehog (October 25th, 1991) for Master System and Game Gear.A remastered version was also released in 2013 for iOS and Android. Re-released in 2005 for Mobile Phones, in 2006 for Wii Virtual Console, for Game Boy Advance as Sonic the Hedgehog Genesis, in 2007 for PlayStation Network, Xbox Live Arcade, and iPod, in 2009 for iOS, in 2010 for PC, in 2013 for Nintendo 3DS in the 3D Classics series, and in 2018 for Nintendo Switch in the Sega Ages series. Sonic the Hedgehog (June 23rd, 1991) for Sega Genesis.
The list only includes games that are titled 'Sonic', with other titles such as Knuckles' Chaotix or Shadow the Hedgehog being considered part of their own series.
