Yep. VGChartz estimates is correct. (Or incorrect since they don't track digital) For example, Nintendo's official website had Pokemon X/Y at 13.99 million units by 30 June 2015. And Animal Crossing is so undertracked it's ridiculous. (Also, Super Mario 3D Land is slighty overtracked) But still, very solid software figures overall from the 3DS.
As for how it might stack up to prior handhelds.
I'd expect the 3DS to surpass the original Game Boy/Game Boy Color in total million sellers. (Right now it's, 38 vs 52) But not in total software overall.
I think it'll be vice versa in Comparison with the Game Boy Advance. I think the 3DS will finish with less million sellers than the Game Boy Advance (38 vs 70), but surpass it in software sales totals.
And I don't think ANY handheld Nintendo makes from now on will ever match the DS in any category.
Hardware Comparison Threads:
Current Thread
Switch 1 '25 vs DS '11, 3DS '17, and Wii '12
Older Threads:
PlayStation/Xbox/Switch: 2022 Edition
PlayStation/Xbox/Switch Hardware Battle: 2021 Edition!
PlayStation 4/Xbox One/Nintendo Switch: 2019 vs. 2020
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2017 vs. 2018
PlayStation 4: 2015 vs. 2016 vs. 2017







