2017. Two of my favorite games: Breath of the Wild and Super Mario Odyssey were released. Also, there was the release of Stardew Valley on Switch. I didn't play it until 2018, but it helps the argument. Not to mention it was the most downloaded title on the eShop for all of 2017. Add in Skyrim (which I'd never played for more than a half hour on my brother's PS3), Xenoblade Chronicles 2, and others. Mario Kart 8 Deluxe I bought begrudgingly, but I enjoyed the new features.
2019 had a lot of strengths, but several slow periods. Not to mention certain flaws of a platform become more apparent when it's been out for 2 years. 2019 was an improvement over 2018, though.
2020 could be the best year of the Switch yet. Animal Crossing: New Horizons will likely be amazing, and BOTW 2 may release. Not to mentioned the rumored Switch Pro or a potential Super Mario Odyssey 2.
Lifetime Sales Predictions
Switch: 125 million (was 73, then 96, then 113 million)
PS5: 105 million Xbox Series S/X: 60 million
PS4: 122 mil (was 100 then 130 million) Xbox One: 50 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