It's Switch, easily.
Now if you want to argue you preferred software or hardware in a different era, that's more than understandable. But Switch has made Nintendo insane amounts of money.
Some may point to the NES and Early Game Boy as more successful but what big competition did Nintendo even have? Switch may be a blue ocean product but it's still competing in some ways with platforms like PS4/PS5, Xbox One/Xbox Series, mobile devices, Steam Deck, PCs, etc. There are so many viable options for gaming nowadays and yet many pick Switch as a secondary or tertiary platform or even the main or sole platform.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
