V-r0cK on 25 June 2018
I'm going to say Pokemon Let's Go. It's been attracting a lot of new players, young and even really old, since Pokemon Go. I've talked with many parents that has like a number of kids that all play PoGo together that are all getting Switches and the Let's Go game. Also, possibly, since this the first Pokemon game that you can play as a home console in a long time might also help.
