This is a difficult one for me, as I still have yet to play Yooka Laylee and the Impossible Lair, which looks like it'll almost certainly earn a spot, and some of my most loved games this year were actually games originally released in prior years that only came to Switch in 2019.
Including those games:
1. Hellblade
2. Witcher 3
3. Luigi's Mansion 3
4. Trine 4
5. Crash Team Racing Nitro-Fueled