The Sega Master System was an 8-bit console initially released by Sega in 1985. It was designed to be a direct competitor to the Nintendo Entertainment System and was technically superior to it. The original Master System models used both cartridges and a credit card-sized format known as Sega Cards. Despite its hardware superiority, it failed to gain significant market share against the Nintendo rival console.
Also, most emulators that run Master System games can run GameGear and ColecoVision, due to hardware similarities.
The Sega Genesis, known as the Mega Drive outside North America or Super GameBoy/Super Aladdin Boy in South Korea, was initially released in 1988. The initial hardware was adapted from Sega's System 16 arcade board and the games were packaged on ROM-based cartridges. The main microprocessor was a 16/32-bit chip which provided backwards compatibility with the Master System games, though due to fears that the load of both visual and audio on the main microprocessor would be too high, they added a secondary CPU chip to handle the sound exclusively.
Eventually, hardware add-ons were added such as 32X and Sega CD and Sega even created two network services to support the Genesis: Sega Meganet and Sega Channel. Overall, it achieved considerable success outside of Japan and established Sega as the main rival of Nintendo in the console war.
The Sega Saturn was a 32-bit home video game console initially released in 1994. It had a dual-CPU architecture and eight processors. Designed around a new CPU from Japanese electronics company Hitachi, there was a second video display processor incorporated into the system's design to better compete with Sony's forthcoming PlayStation.
Its reputation was mixed due to the complex hardware design and limited third-party support. Sega's management had also been criticized for their decisions during the system's development and discontinuation. After the release of the Sony PlayStation and Nintendo 64, the Saturn rapidly lost market share and was discontinued in 1998. Overall, the Saturn is considered a commercial failure.
The Dreamcast was a 128-bit video game console initially released by Sega in late 1998 in Japan and September 1999 in other territories. It was the first entry in the sixth generation of video game consoles, preceding Sony's PlayStation 2, Microsoft's Xbox and the Nintendo GameCube. It was Sega's final home console, marking the end of the company's 18 years in the console market.
Although the Dreamcast had a short lifespan and limited third-party support, many considered the console ahead of its time with a built-in modem and games utilizing various complex accessories..
The Sega Game Gear was initially released in 1991 and had a lot of hardware similarities with the Sega Master System. It was actually capable of playing the Master System games simply via an adapter, which helped flesh out the Game Gear library since it had weak support from Sega.
The reception of this portable console was mixed, with praise for its full-color backlit screen and processing power but criticized for its large size and short battery life. It had some success but was never able to surpass its arch rival the Game Boy.