It's a tie between Pikmin 4 and Breath of The Wild, I love Pikmin and think about it a lot. Probably broke a world record with how fast I unpacked that game and slid it into my Switch!
Breath of the Wild is a game I really would love to play again as if it were new, it gave me such a sense of adventure and desolation that no other game has achieved. I'll sometimes boot it up just to lie down and relax to it
I feel like the WiiU being a handheld is a bit of a stretch! Haha
But seriously though, I keep forgetting that the Switch is a handheld. I like playing docked, and it's too big for me to carry around, generally. But I know I'm in the minority there.
Oh I know Breath of the Wild had a Wii U port haha, I played the Switch version! I've actually never played it docked, I love playing it while in bed or while I'm someplace other than home when I have to wait for a while. Isn't the resolution higher when playing in docked mode?