I'm not sure anyone has mentioned it as a point of support for the stance that games are important but when someone says games are what is selling the Switch in Japan they aren't saying the other platforms have bad games. They're saying that the games released on Switch appeal to the Japanese audience greatly. And maybe it isn't the style of games as much as it is just the brand of games. And we don't need to look so far into history to see that the game theory holds weight. Let's take a look at the Wii U to take away the factor of portability and see how Nintendo's console performed in Japan versus the PS4 and in ratio to other regions. I'm going to use VGC numbers.

Here's a table laying out the region split of sales for the 3 platforms as well as some important ratios. Sales numbers are in millions.

So the big observation is the relative consistency of the region split of sales for the Switch and Wii U. What this indicates is that the Wii U and Switch didn't sell all that different between regions as far as the split of total sales goes. But the Wii U wasn't portable and still sold at a similar ratio regarding Japan vs sales in other regions. The only differentiation is ROW sales being higher for Switch and NA sales being lower but that might be something to do with VGC tracking ROW sales more in more recent years. It could also be lower in NA due to being a portable?  In any case, the result is a strong indication of brand and associated IP being a large factor of why Switch does so well in Japan.

EDIT: I wanted to add more to this thought. The portability and design of the console may have something to do with the popularity of the console as a whole, which is why sales are higher. Meanwhile the ratio of sales between regions remains the same due to the games. So what we're seeing is product design acting as a linear coefficient to an existing game appeal since the ratios for Switch and Wii U are almost exact.

Thanks for the good post.

When all is done a similar breakthrough will give a better view. Because WiiU at 15M sales is very much distorted with the most loyal fanbase when compared to potential 100M sales of Switch.

Similar to a comparison using PSP, PSVita and PS4 would have great caveats.

And yes, I can certainly understand and accept that different games will have different appreciation depending on the public (geographic or platform). But when WiiU had similar type of games but ludicrous sales (still more in line with N64 and GC) while Switch will go near or above 3DS, shows that it being portable, a domain Nintendo have much more strength shows that being portable have helped Switch a lot.

I guess it's the same "big game" idea that happens in most gamers mind: AAA, ancient franchise, current-gen graphics, open world-ish, holywood-sized budget, million(s) seller, sort of everybody likes/buy, etc.

That sounds like you are clinging to cherry-picked data in order to maintain your stance that portability is the biggest factor in Switch's success, but the complete set of data shows that Nintendo has had home consoles that were very successful; the NES sold 19m, the SNES 17m. Using games as the most important factor creates a consistent link between all Nintendo consoles regardless of their form factor.

Consoles that sold more than 15m: NES, GB/C, SNES, GBA, DS, 3DS, Switch (projected).
Consoles that sold less than 15m: N64, GC, Wii, Wii U.

Consoles with good third party support: NES, GB/C, SNES, GBA, DS, 3DS, Switch.
Consoles without good third party support: N64, GC, Wii, Wii U.

The lists are exactly the same. That the less successful Nintendo consoles are exclusively home consoles is not due to their form factor, because if that was the cause, then the NES and SNES shouldn't have been successful. What all Nintendo consoles have in common is good first party support, but the woeful third party support in four cases led to large gaps between worthwhile game releases which in turn crippled sales momentum in the long run. If Switch third party support was shaping up like Wii's, we could conclude that Switch will have a hard time to reach 15m lifetime. But since it's looking like Switch will get robust third party support similar to consoles like the DS and 3DS before it, we have the expectation that Switch will not only pass 15m, but also 20m.

A few days ago I showed you the bestseller lists for Switch and PS4 to demonstrate that Switch has had more hit games than the PS4 and in a shorter time to boot. There's still the question why the Vita sold worse than the PS4 despite portability supposedly being such a big advantage. Let's look at the lists:

PS4 software sorted by sales in Japan
PSV software sorted by sales in Japan

Looks like the PS4 had the bigger games and more of them, so that's the most obvious explanation why it sold more hardware than the Vita.

This post is not to say that portability doesn't matter at all for Switch's success; portability means convenience and that's of course beneficial. But the importance of portability is greatly overstated by you and others, because the data should make it clear that games matter much more for console sales than portability.

I include all data because that approach allows for better conclusions to be made.

And yes, I am going to tell you that the 3DS had more appealing software than the PS2.

PS2
3DS

But no, the PS4 lineup isn't a million times more appealing than the Vita's library. The PS4 game selection skews heavily towards American and European tastes, so the huge advantage that the PS4 has over the Vita in America and Europe doesn't translate to Japan. It's also wrong to say that the PS4 is only 2m ahead of the Vita, because the Vita is done selling while the PS4 still has life left in it; a projection puts the PS4 about 4m units ahead of the Vita in Japan, so at least 65-70% more than what the Vita sold. That is in line with the higher popularity of the PS4 library.

Sounds like sethnintendo and curl-6 are one and the same person.

Not really . ps4 has monster hunter, dragon quest , final fantasy, kindom hearts, and almost every other big Japanese game franchise. looking at PSP how did that sell over 20 million in japan? The software according to vgchartz was abysmal for the Japanese market.  

The PSP had a few Monster Hunter games, not just one like the PS4.

PSP

It also had a few Final Fantasy games, Kingdom Hearts, Metal Gear Solid and God Eater which piggybacked on the Monster Hunter craze. The PSP didn't have a Dragon Quest, but the number of MH and FF games more than make up for that. One thing that the PSP list shows in general is the higher frequency of game releases back then.

Not really. something like nioh, ninja gaiden, bloodborn, and sekiro would be fine. those aren't big franchises, 3 of them are new ip's. just something that takes advantage switch, and doesn't look like a 16 bit game or that it runs on a ps2.