SEGA Video Game Systems (1986-1998)

Sega Genesis

The SEGA Genesis, or Mega Drive as it's known outside North America, was released by video game company, SEGA, in 1988 in Japan, and 1989 in North America. Sonic the Hedgehog made his debut on the Genesis, and it quickly became the best-selling game on the console. The successor to the Master System, SEGA went on to sell 30.75 million units by the time the console was discontinued in 1997. Majesco took over selling the console in 1998, and went on to sell 1.5 million more units in 1998-1999. 

Source: Retro Games Plus 

Sega Game Gear

SEGA released the handheld video game system, Game Gear, in October 1990 in Japan and in April 1991 in North America. The console had a price of $149.99 when it was released in America in 1991. The Game Gear faced heavy competition from the Atari Lynx, Nintendo Game Boy, and NEC TurboExpress. SEGA made the console more appealing than the Game Boy by adding a full-color backlit screen, which the Game Boy lacked. The Game Gear ultimately beat the Atari Lynx and TurboExpress, but couldn't surpass the sales of the Game Boy, selling just 10.62 million units by 1996. SEGA discontinued the console in 1997, but Majesco re-released the system in 2000 under a license from SEGA.

Source: Retro Games Plus 

Sega Dreamcast 

The Sega Dreamcast was released in 1998 in Japan and 1999 in North America. This console was the first console to feature a built in modem for online play. The Sega Dreamcast didn't sell well in comparisson to it's competition, the Playstation 2, XBOX, and Gamecube. With only 9 million units sold, it sold the least amount of units out of the 4 consoles. After sales slowed dramatically, Sega discontinued the Dreamcast worldwide in 2001 and left the console market altogether after 18 years.

Source: Retro Games Plus