1978-1981: Magnavox Odyssey 2, Mattel Intellivision
The four-year stretch from 1978 to 1981 saw the emergence of two significant game consoles: Magnavox's Odyssey 2 and Mattel's Intellivision.
1978: Magnavox Odyssey 2
In 1974, Magnavox merged with Philips and four years later released its own $200 cartridge-based console. Though the new Odyssey 2 (aka the Philips Odyssey 2 or Philips Videopac G7000) had lower specs than the Atari 2600, it produced less-flickery graphics; notable features included an alphanumeric membrane keyboard and voice synthesis.
1980: Mattel Intellivision
For a while, superior graphics and sound made Mattel's $300 Intellivision (and a succession of rebadged versions) the major competitor to the Atari VCS. Mattel's product was the first console to use a 16-bit microprocessor, but poor controllers and--more importantly--a lack of third-party games limited its success. Mattel eventually released an adapter for Atari 2600 games, but the adapter worked only with the later Intellivision II console.