These were all brand new games however. MK8 DX was simply seen a remaster back then. They changed a few gameplay aspects and remade the battle mode but nobody thought of it as a new game. 

But admittedly it just is one of the most fun and accessible type of game on the system

I'm gonna do a top 20 prediction just show how even the 20th best selling game can be a big seller. Doesn't take into account unannounced titles, even ones that are rumored.

1. MK8 DX - 70 million

2. ACNH - 50 million

3. SSBU - 37.5 million

4. BOTW - 36 million

5. SMO - 31 million

6. TOTK - 30 million

7. SV - 29 million

8. SWSH - 28.5 million

9. SMP - 22 million

10. NSMBU DX - 21 million

11. RFA - 20 million

12. Switch Sports - 18 million

13. Arceus - 17.7 million

14. LGPE - 16.7 million

15. BDSP - 16 million

16. MHR - 15 million

17. LM3 - 15 million

18. Splatoon 3 - 15 million

19. 3D World - 14 million

20. Superstars - 14 million

Over 20 games that should easily reach 10 million, and (there are others that could reach it like Mario Maker 2, Kirby and unannounced titles). Over 10 with 20 million and over 5 with 30 million. Two titles exceeding 50 million. Sucks that Arceus & BDSP had their legs cut short. Arceus could have been an easy 20+ million seller.

Pretty decent take on a top 20.

Monster Hunter Rise wouldn't be eligible though as we're talking first party only. If we include third party I'm sure a game like Minecraft is also in the 15m+ club (currently 3m physical in Japan alone, for a game that mostly sells digital), though we'll probably never get confirmation on it.

True, I guess when it came out people may have thought it was a stop-gap port expecting them to make a new MK for Switch. (though no system before Switch had 2 MK games)

Ultimately I guess they did with home circuit, but the mixed reality thing is still a bit niche.

1. Mario Kartio 8 Deluxe (-)
2. Animal Crossing: New Horizons (-)
3. Super Smash Bros. Ultimate (-)
4. The Legend of Zelda: Breath of the Wild (-)
5. Pokémon Scarlet / Violet (+2)
6. Super Mario Odyssey (-)
7. Pokémon Sword / Shield (-2)
8. The Legend of Zelda: Tears of the Kingdom (NE)
9. Unreleased Pokémon game (NE)
10. Super Mario Party (-2)

@UnderwaterFunktown True! In that case, I could see either Splatoon 2 or the next Pokemon game squeaking into the top 20 (I'm speculating that the next Pokemon game will release in holiday 2024 and be a Crystal remake by ILCA).

1. Mario Kart 8 Deluxe – 63m
2. Animal Crossing: New Horizons – 47m
3. Super Smash Bros. Ultimate – 37m
4. Breath of the Wild – 35m
5. Tears of the Kingdom - 29m
6. Pokémon Scarlet & Violet – 29m
7. Pokémon Sword & Shield – 28m
8. Super Mario Odyssey – 28m
9. Super Mario Party – 20.5m
10. Ring Fit Adventure – 17m

If a 2D Mario game comes out like for the holidays (as it should!!) then RFA will get knocked off this list and I think 2D Mario would end up 9th ahead of Super Mario Party.

The new current top 10, and changes last quarter:

1. Mario Kart 8 Deluxe - 53.79 million (+1.79 million)
2. Animal Crossing: New Horizons - 42.21 million (+620k)
3. Super Smash Bros. Ultimate - 31.09 million (+650k)
4. The Legend of Zelda: Breath of the Wild - 29.81 million (+810k)
5. Pokémon Sword/ Pokémon Shield - 25.82 million (+140k)
6. Super Mario Odyssey - 25.76 million (+640k)
7. Pokémon Scarlet/ Pokémon Violet - 22.10 million (+1.49 million)
8. Super Mario Party - 19.14 million (+350k)
9. New Super Mario Bros. U Deluxe - 15.41 million (+660k)
10. Ring Fit Adventure - 15.38 million (+160k)

Quarterly changes:

1. Mario Kart 8 Deluxe – 55.46 million (+1.67m)
2. Animal Crossing: New Horizons – 42.79m (+580k)
3. Super Smash Bros. Ultimate – 31.77m (+680k)
4. The Legend of Zelda: Breath of the Wild – 30.65m (+840k)
5. Super Mario Odyssey – 26.44m (+680k)
6. Pokémon Sword / Pokémon Shield – 25.92m (+100k)
7. Pokémon Scarlet / Pokémon Violet – 22.66m (+560k)
8. Super Mario Party – 19.39m (+250k)
9. The Legend of Zelda: Tears of the Kingdom - 18.51m (NEW)
10. New Super Mario Bros. U Deluxe – 16.17m (+760k)

Mario Wonder sales are going to be stupid big. Launching on a 130m+ install base on the all time greatest system for moving software after the movie just sold 164 million tickets at the box office (!!) and proper new 2D Mario is always the best selling Mario? Yeah, this would be beating MK8 if it wasn’t so late in the life cycle. Probably impossible bc of that factor, but I genuinely think Animal Crossing will go down.