This year
Splatoon 2
SMP
Animal Crossing
Pokemon gen 8
NSMBUD

Next few years

BOTW2
SMO2
Pokemon 3rd version/Remake
Pokemon Gen 9
Metroid(?)
Minecraft

yea but mk8 was out when there were not many games... still its selling crazy

Switch software is doing stupidly well, so I think there'll be plenty of 10m sellers.

My guess would be:

Already There:

Mario Odyssey
Mario Kart 8 DX
Zelda
Pokemon LG E/P
Smash

Released/Announced stuff that will make it:

Splatoon 2
Animal Crossing
Pokemon Gen 8

Stuff that can make it, if marketed properly/recieved really well:

Dragon Quest XI S
Super Mario Party (provided that no sequel is released)

Stuff that is likely in the works that would make it:

Pokemon Gen IV remakes
Pokemon Gen 8 third game/sequel
Pokemon Gen 9
Zelda BOTW sequel
3D Mario
Super Mario Maker

I'm likely forgetting a few big hitters that have a chance, but these are my guesses.

Can we consider lets go pikachu and eevee as 1 game? I dont think so, anyway i think that about 15 titles can make the achievement

Yes, Nintendo counts all Pokemon duos as a single release.

As highly acclaimed the Metroid franchise is, I think reaching 10 million will be a tough challenge. The best-selling game in the franchise has not even reached 3 million units.

The stars will have to align for Metroid Prime 4 (or any future Metroid game) to sell that well. It's not just the quality of the game, it has to have the marketing and convince players to get invested in the type of game Metroid Prime 4 is selling. Part of the reason, I believe that first-person shooters have had success is the fast-twitch gameplay and online multiplayer, which is kinda like watching a high-octane action movie. Metroid, on the other hand, is more about atmosphere, discovery, the single-player experience, and some elements of horror as inspired by the Alien franchise, which, historically, is not a box office juggernaut.

If Nintendo can somehow win non-Metroid fans over to a slower, but unique first-person experience like BioShock, Portal, and Resident Evil 7, then Prime 4 has a chance to be the best-selling Metroid game in the franchise.

It looks like Switch will beat Wii for 10m sellers, insane

Yes, you are correct, it´s considered as 1 game.

So Ive decided to upgrade this thread after a year and a half to see how things are going. adding 4 new titles to the list (Pokemon SWSH, Animal Crossing, Mario Party) for a total of 9 already, any predictions for the following game getting in the top?

btw it already has more games that sold more than 10m than 3ds and also one to beat wii

That is certainly a big number of 10+ Million sellers, great games.