The NES and SNES had a much, much smaller potential customer base. The industry is exponentially larger now. Comparisons to anything older than the Gamecube are meaningless, and even that's pushing it. And the 3DS isn't considered much of a success by business metrics, because you're expected to equal or exceed the hardware's predecessor, which 3DS hasn't even come close to doing.
Predicting failure at this point is silly given how well the system is selling, but predicting huge record-setting success is no less silly. There's no mainstream media hype on the system like there was on the Wii, there's nothing gimmicky to capture the mainstream imagination like the Wii (no, portability is not that, the mainstream is not impressed by portable gaming after 10 years of smartphones), and the system is currently still selling to Nintendo fans and will continue to do so for some time. The Wii U showed us that around 10 million people will buy anything with Nintendo's name on the hardware, so we can't really judge Switch's long term success until those people have Switches and we see how it's penetrating the mainstream market. We may get a glimpse of that this Christmas, but I suspect we won't have a clear picture in this area until sometime next year at the very earliest.
tl;dr - This is a marathon, not a sprint. Calm down.