Nintendo had their first competitor in the United States in 1989 when Sega released their 16 bit Genesis system. However, they still had the biggest market share in the country, and they were about to strike back against Sega with the release of their Super Nintendo Entertainment System in 1991. The SNES was a 16 bit system, just like the Genesis, but it also possessed more overall power than the Genesis did. Because the NES had made Nintendo a household name in the United States, the release of this more powerful console would go a long way in helping them to retake control of the American market. This was when the “console wars” really began to get competitive.
In early 1992, it was estimated that Sega held a 60% share of the 16 bit market (this, of course, does not include sales of 8 bit consoles). This is largely due to the two year head start that the Genesis had over the Super Nintendo, and the fact that, in that time, it was able to build up a much larger library of games. Because the SNES was still brand new at that moment, it was also the more expensive console, which boded well for Sega. However, with all of this considered, one might think that Sega would have been able to take over a larger share than it had at that time.
Nintendo was slightly down upon the release of the SNES, but definitely not out. The two consoles would battle it out for the remainder of their dominance, with neither ever actually taking full control of the market. The Genesis generally did better overall in Europe than the SNES did, but, in the end, the SNES still slightly beat out the Genesis in the United States.