The NES is hands down the best. It had the most original content by far of any console. The following IP were all created on the NES/Famicom:
Super Mario Bros.
Those are some of the biggest franchises in gaming and they were all created on one system. Although in order to appreciate the NES, a person probably had to live through it. Someone looking back will not think that the first Final Fantasy or Metroid or Metal Gear is the best in the series. But many of the games that came later were making gradual improvements and iterations upon the originals. Were the later versions better? Yes (usually), but they were standing on the shoulders of giants.
When it comes to original content no other system can beat the NES. Many people may remember the first time they played GTA3 or Final Fantasy 7 or Minecraft or Dark Souls. On the NES those types of games were coming out all of the time. Every year had several hot new games that felt like nothing you'd ever played before. That it is why it is the best system ever created.
True, except for Tetris, Punch-Out and Metal Gear. The NES is still king though.