Nintendo Switch was the best selling system in the Americas for 7 out of the 10 months it was available and was the best selling system in Japan for all 10 months it was available. It had the fastest first 10 months of sales in the United States, Japan, and several European countries. It was the second best selling system for the whole year in the United States and the best selling system in Japan, despite in both regions, only being out for 10 months.
It currently has the highest ratio of software to hardware sold for its top games like Super Mario Odyssey, Mario Kart 8: Deluxe, and The Legend of Zelda: Breath of the Wild. In its debut year, two exclusive titles for it were in top contention for game of the year and both were critical success stories as well.
On a global scale, much of that is warranted to say that Nintendo dominated 2017.