The Sega Master System had failed to challenge the NES, but with the release of its 16-bit system, Sega Genesis, the company pursued a new marketing strategy. Whereas Nintendo targeted 8- to 14-year-olds, Sega’s marketing plan targeted 15- to 17-year olds, making games that were more mature and advertising during programs such as the MTV Video Music Awards. The campaign successfully branded Sega as a cooler version of Nintendo and moved mainstream video games into a more mature arena. Nintendo responded to the Sega Genesis with its own 16-bit system, the Super NES, and began creating more mature games as well. Games such as Sega’s Mortal Kombat and Nintendo’s Street Fighter competed to raise the level of violence possible in a video game. Sega’s advertisements even suggested that its game was better because of its more violent possibilities (Gamespot).
It's fair that the competition between Nintendo, NEC and SEGA made the companies to produce better consoles. Which is really good for the customers because then they get good products.