Killer Instinct Gold is the Nintendo 64 version of Killer Instinct 2. It was released shortly after the launch of the console. The game suffered some graphical downgrades and the endings for each character do not change (as they would in the Arcade version) due to the memory limitations of the Nintendo 64 cartridge. Other than that, Killer Instinct Gold remains faithful to the original Killer Instinct 2.
Source: Wikipedia, "Killer Instinct 2", available under the CC-BY-SA License.