This x 100
Its weird that we even have to explain this on GAF or more specific on Sales-GAF. The success of a Nintendo platform always relies on the First Party output - depending on that output and the systems success the 3rdParty environment will change as well. At the end of the day a big exclusive game will always have more impact on a system that games that can be played on multiple system, thats the main reason why the PS4 is looking so much better than the Xbox for many people this generation.
At the same time people will ignore "big" games like Fifa. Skyrim, Rocket League when they are coming to Switch because it doesnt fit their personal definition or narrative of what a big or important game is. I can tell you that CoD and GTA V could be announced for Switch for next year - you would still see people that would list a couple of games that arent coming to to demonstrate that there is no 3rdParty support.
We have people often argue that the 3rdParty content support since the Cube has been the same on Nintendo platforms. Honestly if you cant see the difference between 3rdParty offering between Cube, DS/Wii or WiiU you shouldnt even bother.
Just on the point of 3rd-party games, I think there is a qualitative difference, looking at the home consoles of the past 3 generations:
Wii - Series like Call of Duty or say, Dead Rising, see release but in many cases are heavily downgraded from their PS360 counterparts. Other major series like Assassin's Creed or Grand Theft Auto see no release. Later generation AAA titles in particular are very scarce, perhaps since they were pushing the PS360 quite hard already.
WiiU - Seemingly heavy (particularly western) third-party support out of the gate (Deus Ex, Call of Duty, Watch Dogs, Yakuza 1/2 HD, Assassin's Creed) with relative parity to last-gen versions or new PS4/XO versions, quickly drops off and never recovers.
Switch - Timid (Japanese) third-party support (Bomberman, I Am Setsuna, Dragon Quest Heroes, Koei-Tecmo history sims) with a smattering of indies. Essentially zero non-Japanese AAA games since launch, and none announced for the future aside from those which still release on last-gen systems (FIFA) or which are remasters of last-gen games (Skyrim). Rocket League is popular to be sure, but it is no GTA in terms of relevance in the third-party space. There's an obvious difference between the AAA third-party offering on Sony and even Microsoft (Destiny, Doom, Final Fantasy, Call of Duty, GTA, Red Dead, Mass Effect, Yakuza, Assassin's Creed, Ghost Recon, Dragon Quest, NieR, Prey, Deus Ex, Hitman, etc.), compared to what Nintendo is getting.
So more than saying "they're all the same in terms of support", it's more like they've always had the worst offering of third-party games unless you
really hone in on a very specific subset of Japanese titles, many of which tend to also be available on PS4 and/or PC. What's more, this selection only seems to have gotten more narrow as time goes on, and it means that Nintendo home systems are all the more dependent on first-party output to stay afloat. That first-party output can be great, even amazing, but the pertinent question is if it can maintain a reasonable progression outside of the first year.
In many ways Sony has it easy in that regard--it's the market leader of course, but that means that even if the next Uncharted game is hot garbage, PS4 sales aren't going to tank significantly for months, because all the AAA games for console gamers are primarily on that system. It's really just icing on the cake and added value when the exclusives are good (NioH, Last of Us, Persona, Horizon, Yakuza, etc.).