Flilix on 13 February 2017
I think the number of million sellers on 3DS is lower than on PS4 mostly because of the smaller library. The 3DS hasn't much more than 50 games that are actually fun.
Just compare the best selling 3DS games to these on PS4. There isn't much difference there.
But if you go to the 50st best selling game on PS4, you'll see it's Ratchet and Clank, which is still quite popular.
