This is a fundamentally silly argument, because in all previous generations there was a huge overlap between Nintendo's handheld and console markets, so there were many individuals who owned, say, both a DS and a Wii. There's really no incentive for a lone person to own multiple Switch unless they upgraded from the OG Switch to the OLED, but, of course, there were also plenty of people who upgraded from the DS to the DSi or from the 3DS to the New 3DS. And Nintendo is making record profits and selling a massive amount of software without the costs associated with producing and supporting two platforms, so even as a metric of business success your approach makes zero sense.
But, sure, OK, let's compare anyway:
Switch: 103.54 million units and counting
Wii U + 3DS: 89.5 million units
Wii + DS: 255.65 million units
GameCube + Game Boy Advance: 103.25 million units
N64 + Game Boy Color: ~92.28 million units*
SNES + Game Boy = 108. 45 million units*
I'm using this Wikipedia page as my reference:
https://en.wikipedia.org/wiki/List_of_best-selling_game_consoles
So, really, even if you use this absurd, pointless standard, the Switch has exceeded or is close to exceeding all previous generations already, at what Nintendo claims is roughly the middle of its life cycle. The only outlier is Nintendo's obscene, unprecedented success during the Wii + DS years, which you, of course, cherry-picked for your example.
* - OK, I cheated a bit here. Since I couldn't easily find separate Game Boy and Game Boy Color numbers, I divided the total for the family of systems across two generations. This made more sense to me than lumping the entire family in with either the N64 or SNES since the Game Boy line had an absurdly long life that overlapped with both systems. I don't know what the actual sales arc looked like, but I'd guess that I might be underestimating the SNES + GB period and overestimating the N64 + GBC period. In which case, the Switch might not be as close to catching the SNES/GB era as it appears, but it'll certainly get there regardless. Oh well.