Technology has come a long way since Pong and Asteroids. The advances in video games are often astounding and nearly magical, but sometimes the classics are classics for a reason. The new Nintendo systems don't seem to have the same immersion or heart to them. Many people still fondly recall the days of their original Nintendo systems, and refer to it as the best.
While I love the NES as much as the next guy, I defiantly think the SNES upgraded every part about it and more. Of course there was the technical aspects (Better graphics, better sound, more processing, etc.), but also the upgrade in games was phenomenal. Mario 1,2, and 3 were upgraded to Super Mario World, one of the best games of all time. Zelda 1 and 2 were upgraded to Link To The Past, one of the best games of all time. Metroid was upgraded to Super Metroid, one of the best games of all time. And Final Fantasy was eventually upgraded to Final Fantasy 6 (Or 3, depends on outlook). Do you notice a pattern yet? And that's not even scratching the surface on how many great games there are! There's the Donkey Kong Country Trilogy, F-Zero, Earthbound, Chrono Trigger and Super Mario Kart
Nintendo 64 will always be remembered as a classic, and the Wii and Wii U are both excellent systems. The original Nintendo is obviously special, since it was Nintendo's first system, but I think most people remember the N 64 more fondly. More recently, the Wii U is a fantastic system that is my personal favorite, but the N 64 still might rank higher for nostalgic reasons.
Nintendo was a great start in entertainment systems, but Super NES did even more than Nintendo did. The Super NES games were more complicated and had more interesting features. After Super NES the games started to get too complicated to follow, which made Super NES the pinnacle of the entertainment systems.
It's easy to have a lot of nostalgia about the NES. For many adults, it was their first video console. However, Nintendo has worked hard over the years to keep pushing their technology and make sure their systems have something for everyone. There is no such thing as a "best" Nintendo system, because they all have their own merits and innovations.