I usually hate blanket terms like "the best" anything, but let's be honest here, on the NES there was one game that was a shining example of what the machine could do. It had the graphics, it had the speed, it had the music, and it had the two player battle mode. That game was Super Mario Brothers 3.
Released in Japan on October 23rd, 1988, which is 25 years ago, Mario 3 made it to the United States in February 1990, presumably due to all the dialog that had to be translated. I mean, let's face it, with over twenty lines of dialog, this game had probably the most immersive story seen in video games at the time.