I was thinking about this in the talk about Sony and their in-house output concerns from the smaller teams, as well as the old Jimqusition video on how the Xbox launch titles helped establish micro transaction in the paid games these days. 

It makes sense on paper that games that the console provides itself in turn affect what games that console/maker has do well on it. Xbox's historic shooter dominance would have come as a result of the foundation of Halo, while the casual market of the Wii came from how big Wii Sports was. Inter-first party links certainly exist, see the Fire Emblem and Smash relationship for that one. But beyond that....I wonder how much of a relationship there is. 

(Mostly Nintendo fan here, so the following are more Nintendo examples)

Meanwhile I can see an argument on how the type of exclusives Nintendo makes would dampen the appeal of 'mature' games on the platform in comparison. Does the fact that Mario games do well and Knack games struggle affect the viability of platformers on both systems? Do games like Mario Rabbids and Three Houses boost games like Warframe and X-Com? Is the success of Zelda games helping the Zelda-like indie titles? Does Splatoon make games like Fortnite and Overwatch do better on Switch than if it didn't exist? 

...IDK, you guys have any thoughts? 

I'm confused. Do you want to understand if there is synergy between first party output and third party output, hence if a first party start to release too much games for a specific genre other games from that genre will also blossom due to affinity for the first party library?

I'd say yes, but barely. If anything in multiplayer games like Splatoon having competition with Fornite and Overwatch must not be exactly the best idea. I'm not seeing third party platformers or kart racers selling more on Switch just because Switch owners buy a lot of Mario games 

Actually...

We don't have too much data on Switch titles as VGC stopped tracking, but we do have data for WiiU. Sonic & All-Stars Racing Transformed is a multiplatform Kart racer, and it did sell according to VGC the following:

1. X360: 580K
2. WiiU: 530K
3. PS3: 500K
4. Vita: 440K
5. 3DS: 300K

So WiiU is quite good. Given, that the game came late in the life of PS3 and X360, but still a year to the successors and as games often sell frontloaded, they should've had the majority of their sales.

Another datapoint would be Rayman Legends. This has more platforms. PS4 version with 1.5M is far ahead of WiiU version with 680K and the late port for Switch is counted with 690K just ahead, but everything else falls behind: PS3 (610K), X360 (460K), XOne (380K), PSV (160K).

Compare that to other genres. Deus Ex: Human Revolution sold only 110K on WiiU, less than 10% of the 1.38M on both PS3 and X360. Batman Arkham City sold 370K, again less than 10% of the 4.75M on X360 and 5.54 on PS3. Assassin's Creed III sold 360K against 5.31M on 360 and 6.5M on PS3.

Even Resident Evil Revelations, which originated on a Nintendo platform and where WiiU isn't the only one getting a late port of: WiiU only 220K, X360 with 260K and PS3 with 760K. The original 3DS release sold 890K.

So WiiU while not selling a lot and generally not having great sales in comparison to other platforms for multiplat games, was still competitive withKart racers and platformers. So there is at least a hint, that this theory could have some base in reality.

Great points. If platformers and racers were doing well on Wii U despite the system dreadful sales, this maybe has a hint Switch owners are more inclined to buy those genres.

About the other games you mentioned, we need more material evidence still. We something released at all systems at the same time, late ports are overall a bad way to gauge sales

The only good instance to prove your point is indeed RE Revelations where all 3 systems got a year late port. Interesting to point that Xbox performing much worse than PS3 is more noteworthy for me than Wii U sales here (which was actually good considering it's very small userbase). Resident Evil is a very strong brand in Japan, and a classical game for Playstation ecosystem since the 90's, while not quite as big on Xbox 

I'm very inclined to believe sometimes it's more like a console userbase has more familiarity with a specific brand or set franchises than with a specific genre

I think you'd need to do some of the research yourself. This might involve going back to older generations, but we have loads of data from Gens 5 through 7, so you should be able to draw some conclusions from that.

Here is my belief on third party sales.  It depends if the third party game is trying to be "top of the genre" or not.  On the NES there were lots of 2D platformers, but none of them sold anywhere near what the Mario games sold.  At the same time, a developer could make a platformer with a fairly modest budget, and they'd still make a good profit.  They were benefitting from people's love of Mario, so it was easier for them to make a profit.  A lot of people wanted other platformers to play in between Mario games.  On the other hand, the top NES RPGs were the Dragon Quest games.  These are the among the best selling third party games on the NES and in Japan they were actually selling at least as well (or better) than the top first party games.  Nintendo didn't make any RPGs on the NES, so Dragon Quest came in and became top dog.

You can see this sort of thing on the SNES too.  There were lots of platformers again.  However the top third party games were RPGs and Fighting games (like Street Fighter).  Nintendo didn't make either of these genres.  And just recently, the Switch just released Monster Hunter.  We can all see that it is selling like a major first party title, and Nintendo doesn't really make a game that is anything like Monster Hunter.  Over on Playstation, I originally thought the first Uncharted game was a Tomb Raider rip off, but nowadays all of those Naughty Dog Third Person Shooters blow away Tomb Raider in sales.  So basically, I think small budget third party games benefit from picking a popular genre, but the really big sellers would rather not compete directly with a big budget first party game.

I am convinced whatever surprisingly good sales third party games have had on modern Nintendo devices would be even better had said games launched at th same time as the other platforms. When a game comes out 1-5 years later on Nintendo, then almost all the sales you get are the fans and they don't get hardly any of the bandwagon/hype train purchasers. If MH Rise came out on PC first, then in Switch 6 months later, I'm convinced sales would be probably 3-5 million less lifetime on Switch. There are a ton of people that buy things when they are brand new, but don't buy things after months/years of hearing about it (they lose excitement).

" Does the fact that Mario games do well and Knack games struggle affect the viability of platformers on both systems? Do games like Mario Rabbids and Three Houses boost games like Warframe and X-Com?".

That's...really confusing, because for the first part of your example, you're saying that Mario hinders Sony's game, then your second example is pitching that Ninty's 1/2nd party boosts other games, like either way you're putting it, Nintendo's influencing/crushing others, and that isn't really the case here.

Warframe's been around for years and it's being doing well because it's a game loved by many, and that it also happens to be addictive and good for those that play it. XCOM has been around for a very long time, longer than Warframe and that's been popular on PC for as long as it's been around, and Nintendo hasn't boosted that game either, so that example doesn't really make sense.

If this is only about Switch's storefront, then this should go straight into Nintendo discussion, if it isn't, and it's about other platforms and the games selling differently on multiple systems, then the example, again, doesn't make sense.

I agree, that other reasons might result in these numbers. For instance WiiU also had Mario+Sonic at the Olympic games and an exclusive Sonic game, that ight have helped with the Kart racer. My main point is, that I wouldn't throw the theory of the OP out of the window. Problem is obviously, that we have no easy way of comparison. Every game sale comparison has downsides. So it will not be easy to decide if an effect like the one described in the OP is real or not.