But you said there is a huge amount of overlap from Wii and DS owners. For that group who owned both (50 million? 60 million? 70 million? 80 million?), it doesn't matter if its one or two devices... they bought a lot of games for both devices.
And about the 13/14 years: the biggest part of these games was sold in a much shorter period: 890 million DS games and were sold in a six-year-period and 840 million Wii games were sold in a six-year-period, so 1730 million games in total.
It's still 2 separate devices. I bought more games across Wii and DS than Switch because they were separate devices. I bought New Super Mario Bros (DS) and New Super Mario Bros Wii (Wii). But I'm not about to buy New Super Mario Bros Deluxe (Switch) twice just to keep up with my purchase rare on the DS and Wii.
You should really look at it from a software to hardware attachment ratio.
Wii - 9.06:1
DS - 6.16:1
Switch - 5.9:1
That Switch figure is far higher than either Wii or DS at the same point in their life and already about to pass the DS.
Massimus - "Trump already has democrat support."