When was the last time Pokemon sold over 20 million, though? The last time that happened before Sword/Shield did it was in Gen 2, (Gold/Silver), back at the tail-end of the original Pokemania Phenomenon, back when Pokemon was the biggest thing on the planet. And now, it's just 2.01 million units away from passing Gold/Silver for 2nd on the all time list. And who knows? Sword/Shield has shown to have much better legs than Pokemon games of the past. If it doesn't reach Red/Blue, it could come pretty damn close. And that would all be IN SPITE of the quality issues that you mentioned... So, the software itself doesn't seem to be that big of a factor, albeit an important one, just like the system it is on, among other factors that I described.
And I'm not sure what you're trying to say regarding NSMBU. Are you saying it WILL be the best selling 2D Mario game even without the Wii U sales? If so, you're just proving my point.
But, yes, you are right that the software itself is an important factor. But, there are other factors that are just as important into making it a hit, which I have detailed in my last 3 posts. All of which Dread should have going for it, which is why it would be a disappointment if it doesn't achieve similar feats as other games from other franchises that have been in its position.
You say no software is guaranteed to sell well until people have actually seen the game. Well, we've all seen it and the reception has been overwhelmingly positive. Quite the opposite from Sword/Shield where that game was panned by a lot fans pretty much from the start. Dread clearly passed the '1st impressions' test with flying colors. And if you've played Samus Returns, then you have a very good idea of what the game is going to be like considering it's made by the same developer. But unlike Samus Returns, this is on a system in its prime, a system that's white hot, and being positioned as a major, top-tier 1st party entry on that system. So, it should achieve record-setting numbers by the franchise's standards. If you're a Metroid fan, I don't see how you wouldn't demand anything less.
I meant NSMB U shall not be the best selling 2D Mario even when we combined Wii U and Switch sales, simply because it's not a very good 2D Mario. It may not surpass New Super Mario Bros for DS either
But you are right things are doing good for Dread, that's why I believe it has solid chances of being the best selling 2D Metroid yet, but it fall short I still don't think it's enough to "doom" the franchise. Metroid treatment has been abysmall, at this point the franchise isn't that popular. I agree fans are satisfied and happy, but fans aren't enough. Dread trailer has only 800k views on YouTube, that's solid and about 2 times bigger than let's say SMT V and WarioWare, but it shows Metroid brand is closer to this range of popularity (SMT and Wario)
Even if the fandom like it the casuals just don't care and very likely keep not caring until the game came out and have great reviews and great WOM
Does it means the franchise has no potential? Not really, it just means GP isn't really aware or bothering with a 2D Metorid yet and maybe just one game won't be enough to turn things around. I'm just saying to not be so harsh if Dread does not meet your sales expectations