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).

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.

Agreed, except maybe Super Mario Party, unless Super Mario Party turns out to be the best Mario Party in years.

Nah. Pokemon Let's Go isn't going to bring in non-gamers who played a free to play mobile game. You think they are going to go from a free mobile game to dropping $360 + tax to get a Pokemon game that's called "Go" but doesn't have the main feature that made Pokemon Go a viral hit. Not a chance in hell. Not to mention most of those people stopped playing Pokemon Go in 2016.

Pokemon Let's Go will sell to devout Pokemon fans, just much less so than the mainline Pokemon game that is coming next year.

Pokemon Let's Go is the Wii U of Pokemon games, its the "sequel" to a huge success but is a half measure between two great ideas and doesn't have that exciting new way to play that made it go viral ("play pokemon out in the real world wow!", "play with motion controls wow!" --> "play pokemon on a console but with the dumbed down mechanics of mobile for no reason...meh", "use motion controls but have this single large awkward controller with a screen....meh". Wii U was a halfway measure between the two huge successes Wii and Switch. Pokemon Let's Go is the halfway measure between playing Pokemon outside with simpler casual mobile gameplay and getting the first console version of Pokemon which fans have been wanting for a long time - those two separate things are brilliant, but the half-way house that is Pokemon Let's Go, taking it to console and then taking out all the stuff that made Go exciting and keeping in all the stuff that made sense only on mobile is blaaaahhhhh.

Pokemon Let's Go I'm sure will sell at least 5 - 10 million purely based on the Pokemon brand name and the fact that the Switch is super hot (and probably because its the first AAA Ninty franchise release since Mario 13 months prior), but it isn't gonna be bringing in casual mobile non-gamers and it isn't a substitute for a mainline pokemon game, which is why the real one is coming next year. A portion of huge Pokemon fans will buy it, which could still be like 10 million, as they wait for the real thing a year later.

I think you make a good point that applies to about 99% of Pokemon Go players.  But all you need is 1% to buy a Switch to get an additional 6.5 million people.

Of all the people who ever downloaded Pokemon Go sure. But of the people who still care about it today, that 1% would bring in what like maybe 20k people. The hundreds of millions of people who haven't played Pokemon Go in two years are not going to be thinking about paying $360 for another pokemon game that isn't anything like Pokemon Go but has "Go" in the title, not even 1% of them, the vast majority of them won't even know Pokemon Let's Go exists. And honestly the people who are still playing are all previous pokemon fans. So really that 6.5 million number that went down to ~20k in reality goes down to roughly zero. Like I said, a pokemon game that has "Go" in the title but doesn't have anything that made Pokemon Go a viral hit, and isn't a free to play mobile game, is not going to be picking up non-gamers who played Pokemon Go a couple years ago. Pokemon Let's Go will appeal to a portion of the normal Pokemon crowd, that is it. It will sell well off the brand name, but the mainline Pokemon game coming a year later will outsell it several fold likely.