One notable trend with the Switch that has emerged is that software sales for Nintendo's own games are the best they've ever been. Not only are mainstays like Mario, Zelda, and Smash Bros. breaking series records. But ports are regularly outperforming their Wii U counterparts, and even niche oddball stuff like ARMS and Astral Chain are able to pull a solid 1-2 million copies.

What about the Switch is making Nintendo's software soar in sales? My take is simply, how the Switch presents itself. The Switch is designed to be a device meant for games before anything else, aimed at anybody and everybody who plays games. Regardless of what you want, there's at least something about the Switch anybody can gravitate towards. Unlike the Wii, which was pegged with a "Casual" stigma that it was never able to fully shake. The Switch works well for both novice and dedicated gamers, and thus games of all kinds are able to find a home on it.

I honestly think software sales this strong is also what allows Nintendo to take more risks with their games. When even something as odd and Japanese as Astral Chain can debut at No. 1 on the UK charts, what do have to loose? Sometimes people think that less success means companies take more risks as that means they need to find something that might stick. But I find this to be untrue a lot of the time as it only really applies to companies who never really had many hits in the first place. In cases like Nintendo, its the opposite. You can see this as recent as the Wii U, where Nintendo began doubling down on established franchises because software and hardware sales were underwhelming. Or in an non-Nintendo case, Sega, who announced recently that they'd be focusing primarily on its established core franchises going forward due to poor software sales. Point is, when your making a lot of money on the best software sales you had in years, might as well spend some of that war chest on weird shit too.

Accessibility?

for myself personally it's because I love gaming on a big screen (use a epson full HD projector @ 160") and I love portable gaming, and until the Switch appeared the best portable device going was the Vita which had the same amount of support as a castle built in a swamp. Don't get me wrong the Vita is an amazing piece of hardware and I feel it does have tons of great games, but they're all just wannabe ports of their big console brother counterparts, there are very few direct ports of titles from the other consoles, when it comes to buying software on the Switch in my head I almost feel like it's all half price because before I would have been buying the ps4 and vita versions of a game (if crossbuy wasn't on the title) and at the same time I would be getting a far worse version of the game for the handheld. On Switch a game is 60e but for me it's a 2 for 1 deal compared to last gen, it really takes the sting off getting a new game when you see it like that.

Also the reason that Switch can easily sell more with slightly weaker or what would be niche titles compared to those same games on the WiiU is easy, the system is selling like hot cakes and already has an install base of more than double what the WiiU sold over its whole lifetime, a game can perform half as well on Switch and it will still outsell its WiiU counterpart. The success of the machine is why you're seeing more and more third party support and now there is less need of Switch port begging and we even see companies who had said "fu" to a possible switch port like Hat in Time are now eating some humble pie and putting their game where they know there is money to be made.

I want to be optimistic about Astral Chain's sales as anyone, but let's be honest, the use of it's #1 status on the U.K. charts is really dishonest here. #1 doesn't mean anything if the sales for all software are quite tame in that period. It was only PlatinumGames' 4th biggest launch in the U.K., it was beaten by Bayonetta 2 on the Wii U there. 

Don't get me wrong - digital sales will put it ahead and yadha yadha, it will probably pass 1 mil, and it could even see a massive increase from Bayonetta 2 in territories such as NA. But in the end that #1 figure should really not be used, because it's completely relative. 

The Switch's userbase is older than prior Nintendo systems and has more core-centric and enthusiast gamers. That will lead to higher software sales and a more rabid buying base.

Every 5 years that passes, Nintendo gains more and more adult fans because every generational cycle sees more Nintendo fans who were once children graduate up into adulthood and a certain number of those people are "Nintendo lifers", so that portion of the fan base grows every year basically. 

I don't really buy that. The Wii and DS had high software sales as well. I'd say the Switch has less of a stigma attached to it than the Wii, which for most of its life was (unfairly) pegged as little more than a "casual" system, which caused a lot of "Core" games to suffer on it. Compared to the Switch, where all kinds of games succeed on it. Core, casual, and anywhere in between. Besides, I don't think a hardcore-focused console would come with detachable candy colored motion controllers as the default.

Wow, such a serious gamers machine /s.

If a person pays careful attention, then they will find that there are actually a lot of potential gamers out there that are only being marginally catered to.  The two markets for console gaming are the home market and the handheld market.  But within those two markets there are a variety of customers.  There are always some people on the high end who think, "this is nice, but I really wish it were even better.  I'd definitely pay more if this were better."  There are also people on the low end who think, "That looks really nice, but it's out of my price range.  If the price drops enough then I'll definitely buy, but it's just too pricey right now."

What the Switch is doing right now is that it is appealing to both the low end of the home market and the high end of the handheld market.  On top of that it is extra appealing to people who are in both markets.  So let me describe these three groups.

1) Low end home - These people are buying Switch for Nintendo first party games.  The PS4 or XB1 can basically be found for the same price (or possibly cheaper).  But there are people who will buy a Nintendo home system for first party games and these people are included.

2) High end handheld - These people are extremely happy.  The choices last gen were the Vita or 3DS.  Switch hardware is so incredibly better than the 3DS.  For example, 3DS games output in 240p while Switch handheld outputs in 720p.  It's like handhelds skipped a generation.  Because of this Switch can also bring new types of games to handheld gaming like Zelda: Breath of the Wild.  Vita users are also very happy (like Ganoncrotch said a few posts ago).  It's a more powerful system, but it also has a much better game selection than the Vita had.  Happy customers are also more likely to buy more games.  A person who plays Switch only in handheld mode is going to buy more Switch games this generation than they did 3DS or Vita games last generation.

3) People in both home and handheld market - These people are probably the happiest of all, because they get two systems for the price of one.  There are people who bought 3DS and Wii U.  For these people buying a Switch means they basically bought a Wii U and got a 3DS for free.  Same goes for everyone who owns both a PS4 and a Vita.  The "two systems in one" means they are getting a really huge value.

So, these are all the people that the Switch is currently attracting, but there are more it isn't getting yet: high end home, mid-range home, mid-range handheld, low end handheld.  When the Switch Lite comes out, then Switch will get the mid-range handheld crowd.  This is an even bigger chunk of the handheld market than they are getting now.  I don't know if Switch will ever become cheap enough to get low end handheld.  It needs to drop to $100 or less, and I don't know yet if Nintendo will let Switch get that low in price.  Switch will never, ever get the high end home market.  It just isn't designed for that.  However, in a couple of years Switch will have a huge library of games and PS5 and Scarlett will have $500+ price tags.  I think at that point most of the mid range home market will buy a Switch.

So, basically Switch is getting the Wii U market, and the high end 3DS and Vita market.  And the people in the high end 3DS and Vita market are extremely happy with the system.  They are getting a very powerful handheld system with a great library of games.  As a handheld the Switch is a huge step up from the offerings of last generation, and that is why people are happy to buy more software than before.

Exactly! I've been saying for years that Switch is like a Wii U, 3DS, and Vita combined. 

I call it "beign a compelling system".

Great software tends to sell well. The Switch has some amazing exclusives.