I updated the OP with current numbers. Thanks to the VGC-team for fixing the problem hindering new data and get the numbers flowing again. I think you usually get too less credit for the work you do for keeping the site running.

This week was interesting, because it saw many new releases. In difference to the past, this consisted of releases head-to-head instead of late ports. So the first week data is actually more interesting. The games in question are the Street Fighter Anniversary Collection, Harvest Moon, Owlboy, BlazBlue Cross Tag Battle, The Liar Princess and the Blind Prince and Sega Genesis Classics. Aside from Street Fighter sadly the games all missing at least one platform. Sega Genesis Classics aren't coming to the Switch, the others not to the Xbox. Of the games only Street Fighter broke 100K, although the sales indicate that Harvest Moon should get there soon, and BlazBlue so far only released in Japan, the releases in the other regions should improve sales too.

This are the market shares for the games:

As you can see, the performance strongly differs from game to game. Street Fighter dominates on PS4, is strong on Switch and weak on Xbox. We have so far few data for fighting games among all three platforms, but this collection also thrives on nostalgia, so it is hard to conclude how the sales are influenced by these factors. BlazBlue gives some indication for fighting games, but keep in mind this so far is only japanese data and missing the Xbox. BlazBlue though shows a strong dominance for PS4 with nearly three fourths of the sales on that platform. Sega Genesis Classics can indicate nostalgia sales, but this is missing Switch. Here PS4 dominates even stronger with more than three fourths of the share.

Harvest Moon is interesting, as we have so far few games with the simulation genre among these platforms. No Xbox-release though only let's draw conclusions for PS4 and Switch. Here Switch takes the cake, with more than 70% of the share.

Owlboy once again shows the sales strength of Switch for Indies and platformers. Over 80% of the sales are going to the Switch.

The Liar Princess and the Blind Prince is a port of the Vita-game. As a japanese-oriented game it misses the Xbox. As many other games it shows that for publishers PS4 and Switch start to replace the Vita as the platform for japanese centric story driven games. The sales are interestingly very balanced between PS4 and Switch, nearly identical.

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I added a new graph to the OP. This shows how many games on each platform are selling more than 10%/20%/30... market share. It shows a bit the PS4-domincance in sales. I'll keep that updated in the future.

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I also want to show another interesting development in sales. The game BattleChasers: Nightwar (a pretty classic turn-based RPG) was released as a late port on Switch and shows there incredible sales strength. I think THQ Nordic is kinda pleased with these sales. In three weeks the Switch version already overtook the XBox One version and if the strong sales continue will not take long to catch the PS4 version.

Unless this very steep curve for the NS version decelerate soon it will have more than 50% of the sales very soon.

Yeah, Switch-versions do often not bad. What is more interesting: the split between PS4 and Xbox seems more even, it has smaller differences with different games. But with Switch it wildly fluctuates. Some games like South Park or FIFA have a really small market share, others like Sonic, Resident Evil, Attack on Titan or Disgaea have a real big market share. This clearly shows that the userbase of PS4 and XBox is pretty similar, while the Switch has a very different userbase.

Yes, this is something I again and again say. Sure, a bigger install base usually leads to bigger sales. But it is far from a linear connection, often even a negligable difference. A fan of Monster Hunter gets Monster Hunter, regardless of the platform. The only reason for smaller sales on smaller install bases might be a reluctance to get said platform for just one game.

A few games though grow more with the install base. Seemingly few buy a Nintendo platform for Mario Kart, but many buy Mario Kart if they own a Nintendo platform. So this is a game that grows with the userbase. But even for Mario Kart it is far from linear, and I think there are very few games like that.

Yeah, this sales curve is kinda strange. Most of it is done in the US, in europe Battlechasers sells on Switch around the same as the PS4-version and has the same dropoff. In the US the sales are really big and more baffling stay nearly constant. I don't know the reason, maybe ads?

Oh no. This demand is flawed on so many levels. First of all, it ignores digital sales on other platform, as if Playstation is the only platform with digital sales. Secondly this changes over time, a recent post in a thread here showed, that these numbers are increasing over time. Third, the ratio often includes digital only titles, which inflates the ratio that in result cannot be applied to games that release both physical and digital. Fourth, the digital ratio also fluctuates strongly between different titles. So do Monster Hunter World and Octopath Traveler have a higher digital ratio, because they were initially undershipped.

So in conclusion: if you have data that shows digital sales for the games for ALL platforms (not include PS4-sales digital, but has Xbox only physical or so), then we can make graphs based on that data. As long I can only map data which we have. You have to apply your usual consideration regarding VGC-estimates of physical sales.

The same thing would have to be done for Switch and Xbox One. But we don't have any hard numbers that I've heard about their digital attach ratio.