One of the very first consoles distributed by Sega, before Sonic the Hedgehog even existed until he dominated the company, the Master System was released in October 1985 as the Mark III in Japan, followed by in September 1986 in North America, and in 1987 in Europe.
Like the NES, the Master System can fit up to two controllers. However, there are now three buttons on the system itself -- a power switch button, a reset button, and a pause button. And there is no lid on the console; you just insert the cartridge into an input slot. The controller comprises of a Control Pad on the left, and "1" and "2" Buttons on the right. The Sega logo is also labeled on the controller.
Prior to Sonic the Hedgehog, Alex Kidd was Sega's unofficial mascot since 1986, and starred in his own game, Alex Kidd in Miracle World. During his years, Alex Kidd only appeared in one game for the Sega Genesis, and that was Alex Kidd in the Enchanted Castle, released in February 1989, just after the Genesis was introduced as the Mega Drive in Japan. Alex Kidd was around until 1990, when Sonic the Hedgehog replaced him as Sega's official mascot in 1991.
Nintendo vs. Sega
During the Master System's years, the Nintendo Entertainment System competed with Sega's Master System. Of course, sales of the NES were far more successful than the Master System in Japan and North America, and sales began to decline in 1988 after the release of the Mega Drive.