You examples don't make any sense.

Pokemon S/S is selling huge numbers. Yeah it's not going to beat the original Pokemon, but no Pokemon has come close to that, and S/S will obviously be the second best selling Pokemon game ever. So if you think it is a terrible game that pretty much proves your whole argument wrong. Of course it isn't a terrible game, but anyway this example doesn't make sense.

And NSMBU....ummm there are numerous 2D Mario games that NSMBU:D won't even come close to, so I have no idea what you're talking about there. But considering it was a low marketed port that Nintendo just threw out there in January and isn't particularly great for a 2D Mario game its sales have been phenomenal.

Basically, Nintendo IP have monster sales on Switch. 

The problem with Metroid Dread is its a $60 game. At $40 (which is about what feels right for a first party 2D side scroller not called Mario), I think it could sell around 3+ million which would obviously be great for a Metroid game. At $60 I definitely see this being limited to 1.5 million, and the only reason it'll get that high is because it's on the Switch. I certainly won't be buying it at $60 even though I'd love to play the game, and I'm guessing by the time it is on sale for say like $30 I'll already have MP4 and won't even be bothered about getting Dread. This is gonna be like Link's Awakening remake. Great game that lots of people are excited about but launching at $20-$30 higher than what makes sense so sales are going to quickly die after the first couple weeks on the market.

Franchise is of course not doomed no matter what happens, but sales will be low because of pricing. If they priced it right, combined with the pent up demand for Metroid, plus Switch's install base, I think it'd sell really well. MP4 will be the true test of Metroid's popularity. With the critical popularity of the Prime series, the years long wait for it, and Switch's well over 100 million user base by the time it comes out, MP4 will hopefully go after 10 million in sales thanks to the Switch boost.

Well, you laugh, but even the chance for your statement isn't zero, ain't it? 

I will also say this: For the sake of the franchise, this game HAS to be the best-selling game in Metroid history; Or if nothing else, the best-selling 2D game in the franchise.

This game has absolutely everything going for it as to why it should.

- It has the hype, anticipation, and support from a very hungry fanbase. As evidenced by the high pre-orders and sold out Special Edition a day after the reveal.

- It has the quality or at the very least, it has the potential to be that upper-tier, fantastic game that is ranging in the high 80s-low 90s on all the review sites.

- It has the marketing and full support of Nintendo, to the point where they even have Samus as their profile picture on their Twitter account and they're posting tweets and notifications about the game non-stop. So it is CLEARLY a high priority for them to put this game out there.

- And last but not least, it is on the Switch. How many times have we heard, throughout these past 4 years, about a franchise that had a game release on the Switch and that game went on to become the best selling game in the franchise? 3D Mario, Mario Tennis, Mario Party, Luigi's Mansion, Zelda, Animal Crossing, Splatoon, Xenoblade, Pikmin. And if they're not the best selling entry, they're getting close to it (Mario Kart, Fire Emblem) or are selling at levels the franchise has not reached in a very long time (Pokemon). Hell, even 3rd parties are getting in on the action! Monster Hunter Rise is on pace to become the best-selling 3rd party game on ANY Nintendo system EVER...

...So, why can't the same thing be true for Metroid?

As far as I'm concerned, the absolute bare minimum, the floor for Dread, should be passing Fusion. So >1.6 million. That's the floor. That's the bottom end of the spectrum it should meet. If that's all it manages to do, it would be a good accomplishment, but not nearly enough of what it should be capable of. 

This is the first brand new 2D Metroid game in 19 years and the first new game in the franchise since Other M, which was 11 years ago. And not only is it releasing on a successful system, it is releasing on what could very well become the best selling video game system of all time IN THE MIDDLE OF ITS PRIME!!!

So, as far as I'm concerned. This is it. This. Is. It. This is do-or-die. There are no more excuses. This isn't a case where it's releasing on a system that was clearly on the decline and on its way out like the 3DS with Samus Returns. Or a case where it's releasing on a system that didn't do too well or was a borderline stinker in sales like the GameCube with Prime 1 and 2. This has every single thing it could possibly have going for it to succeed. If you're a die-hard Metroid fan who wants the series to succeed, to achieve greater and higher levels of sales so that Nintendo will take it more seriously and treat it as a higher priority so that we get more games being made, you could not ask for a much better scenario than this.

If Dread or Prime 4 STILL can't do it with all that going for it, then there is just no hope for the franchise. I'm sorry. No hope and no more excuses. This is it. This is the moment of truth.

Before BOTW, no Zelda game had ever sold more than 8 million, now BOTW is on track to easily triple that; never say never when it comes to the Switch, it would not surprise me if Metroid Dread becomes the best selling game in the franchise to date.

While I agree with never say never you have to factor in BOTW became a different kind of Zelda game to be in its situation. Dread can be great but at the moment doesn't look like it has deviated in the same way from prior games like BOTW did although that said I feel like now is a good time for Metroid.

NSW momentum is also a thing and can help it become the best selling Metroid game, I feel Prime 4 could become a mainstream hit when it arrives as modern tastes would be more receptive to it. 

I hate to say it but if this game doesn't sell well, and Metroid Prime 4 also doesn't sell well, I don't see any reason for Nintendo not to drop the franchise. I can't blame them anymore if that happened. The last few games all had pretty convenient excuses to sell poorly - and the fact that the series saw it's boom during the GBA/Gamecube era where Nintendo was putting the most effort into it, rather than the Wii/DS era where Nintendo was at their most popular (prior to the Switch), seemed to indicate some level of innovation and care that made Metroid more popular back then.

But there's literally no excuse now. Up till now I haven't even agreed with the "Metroid fans are lucky to have Nintendo because Nintendo treats Metroid a lot better than any other publisher would" argument (just such a ridiculous hypothetical that even if entertained I could poke a ton of holes in it). If the franchise dies on Switch though, so be it. It would be deserved with low sales of these two games.

What would you consider low sales? Not making the money back? Under 1 million?