It depends. Personally speaking, the prospect of a new generation of the old Pokémon formula doesn’t appeal to me in the slightest: I’m not a big fan of the chore-like grinding, or the obtuse mechanics of comparing a Pokemon’s stats to those of an online database to find the right IVs (because leveling one with the wrong ones are a big waste of time), or the capture mechanic of getting a Pokémon down to 1-3 hp without killing it in order to have a chance at capturing it.

Let’s Go seems to fix every issue - it’s focus is on the main Pokémon rather than a bunch of knockoff content dumps. It maintains the story and regular battles while shedding all the chore-grindy battles: the capture mechanic is a lot more intuitive and with the co-op it also looks a lot more fun. The prospect of playing Pokémon Go with my kids (and wife) looks like a far more rewarding experience o me than the next game will likely give - and I can’t be alone on feeling this, I think a lot of other people are going to see the appeal of the Let’s Go games after the next “regular” Pokémon game comes out; it could very well be selling millions beyond 2019.

Really the only thing I find disappointing about Lets Go are the graphics, they make the game look a little cheap, but as with Fire Emblem Switch, I’ll get over it quickly. Unless the upcoming “regular” Pokémon game has significantly better graphics, I don’t see it stealing much of Lets Go’s longevity because I don’t think the content or mechanics will be able to do it.

Well obvious answer would be Smash Bros, Pokemon Lets Go also has chanches but its legs could be cut buy new Pokemon game next year.

Smash. It's going to be the best selling game in the franchise ever and is the most hyped Switch game since Odyssey (I'd say hype levels trump Odyssey even). Pokemon Let's Go will sell decently, but the new game next year will cut it's legs. Mario Party is a bit of a dark horse, it's looking to be much better quality than the last few entries in the series, and on the Switch it's a perfect fit, I can see it doing 5m+, perhaps greatly exceeding that, but only if Nintendo market it well.

I feel like everything you said is wrong. You're entitled to your opinion and who knows maybe somehow you will be right, but seems incredibly unlikely. Pokemon Go was cool because you could play a game while out on a walk, and you could play pokemon outside and had to actually get outside and go for a walk to play it. And what helped it be cool was that if you live in any city that summer it came out you would undoubtedly run into throngs of other people out playing it, which just made you feel good about being part of the group. In terms of gameplay it was very shallow though, if you put that gameplay in a game but take out the walking around outside-play part it loses its appeal. Hell just take out the group-feeling of seeing everyone else out playing it as well makes it less interesting. There is a reason that it was wayyyy more popular the summer it came out and then its fanbase died out within a few months (granted plenty of people still play the game but nothing compared to that initial summer.

You may not like classic RPG gameplay but that it what the Pokemon fanbase likes. Pokemon Let's Go will probably have more to it than Pokemon Go, but if the capturing pokemon is the same shallow gameplay, which it seems to be, it will not hold the interest of people for very long. It will still sell strong simply off the Pokemon brandname and perhaps some people like yourself that think it'll be revive the popularity of Pokemon Go (it won't), but yes the next core Pokemon game will be far more popular and will likely outsell Pokemon Let's Go several times over. Pokemon Let's Go is the sideshow to give Pokemon fans something to do as they wait for the game they are all waiting for next year (and because Nintendo had nothing else big this year other than Smash).

A new (not a port) 2d Mario!!

Smash and Party will sell for years.

Pokémon Let's Go will be replaced after a year so will probably fail to have the same reach, but whatever they replace Let's Go with will fill that gap.

The game after that will probably be the Switch's 2D Mario platformer title.

I feel like we are overdue for a new Animal Crossing game, and the Switch is seemingly a great console for it (although what game isn't great for Switch, amirite?)

Animal Crossing is absolutely an evergreen title, just look at the legs on the 3DS game. Now they just have to release it... still waiting...

Pokemon Let's Go will be the big Blue Ocean title on the Switch.  This is a far better idea than either Labo or 1-2 Switch.  650 million people downloaded Pokemon Go.  If Nintendo can even convert 1% of that, then that is 6.5m new people buying a Switch.  The purpose of Pokemon Let's Go is to be a bridge between the mobile game and the mainline Pokemon franchise.  I.e. Nintendo wants to take these 6.5m new people (or how many ever there actually will be) and convert them to the mainline franchise.  It's not going to be a half-assed game.  It's going to be very appealing to Pokemon Go players.  On top of this a decent chunk of the current Pokemon fan base will also get the game.

So I think Pokemon Let's Go will sell decently at launch, not like a mainline game, but still good compared to most other games.  Then I think it will have very, very long legs.  This is the Blue Ocean title the OP has been waiting for.

Other than that the evergreen titles are the usual suspects:
Smash Bros
Mainline Pokemon
2D Mario
Animal Crossing

I also am liking what I am seeing out of this Mario Party game.  I would not be surprised if it becomes the best selling Mario Party yet.

Although, your disagreement is based on untrue premises.

1. These are not console versions of Pokemon Go minus walking. They are remakes of the original Pokemon game with additional features and upgraded graphics.
2. They did not get rid of the classic RPG battles. The battle system is still there; both single and multiplayer.
3. A more intuitive capture mechanic is not the same thing as more shallow.

Also, assuming I might dislike classic RPG gameplay is very very much in the direction of an incorrect assumption. =D