Why compare them to NES sales at all?

I'd go further than that - VR headsets have only been properly selling for about two years at this point. The Oculus Rift didn't officially launch a consumer version until mid-2016, as did the HTC Vive, which launched around the same time. While Oculus headsets have been available in some form for five years, everything before the 2016 launch were prototype development-kit versions that came with a big asterisk on the order page saying they weren't meant for general consumer use.

Lots of enthusiasts did buy the Oculus DK1 and DK2 Rifts, but CV1 was the first time it was actually available in stores and marketed as being ready for consumer use.