As a game series, Pokemon may be a bigger system seller than MK8. Early on, BotW was a huge PR point for the Switch and thee game to get, but that quickly changed, and its attach rate was ultimately in the low 20%.

The theory that BotW sold more systems than any other game isn't really backed by anything. Millions of people who bought the game at launch were going to get a Switch anyway, if not at launch then sometime later.

It's bizarre how many people undersell Mario Kart. Some even downplay MK9's ability to sell Switch 2's.

Cheeky answer but the combining their home and portable developments. Instead of Dread, LM3, AC and FE being on a different piece of hardware, everything is under one umbrella. Meaning Nintendo had a nice consistent output.

BOTW is the only game to at one point have more than a 100% attach rate on a platform, this was in the first four months of the S1's launch, nothing screams system seller more than that as people were buying the game even before they could get the platform due to shortages and mind you the S1 had sold around 5m at that point so the game had already passed the then average sales range for the franchise while achieving that. Even with the drop in attach rate later on 20% on a 155m userbase still says system seller as those are huge numbers.

Pokemon as a franchise is a bigger system seller however BOTW in itself can be said to be on par after all it has outsold every Pokemon game highlighting it was still thee game to get years later only three games have outsold it on the platform.

The argument for BotW isn’t that it was the biggest system seller, but that it made clear that Nintendo hadn’t lost their touch. It restored consumer confidence, it gave momentum to Switch, and had the system launched without, no doubt Switch 1 would’ve struggled to cross 10 million by the end of FY’18… a bunch of Wii U ports and Mario Odyssey would not have moved systems.

Mario Odyssey I feel definitely would have (and did) move systems, but that arrived 7 months after launch, so yeah I do think sales would be considerably lower if not for BOTW's breakout success.

The one the only. Vroom in the Night Sky. I AM STARDUST!

Pokemon is near annual, I think you'll agree that individual game comparison to BotW doesn't quite represent each title's significance. It'd be like arguging GTA is several times bigger than CoD because GTA5 will over 250 million lifetime vs CoD's average 30-35 million (and like 15-20 million on Playstation).

BotW was definitely a big deal that contributed to Switch's success, it's foolish to argue otherwise. But it wasn't bigger than MK8D or Animal Crossing. It's also safe to say that it's the kind of game that appeals to consumers outside Nintendo's typical fanbase, who will not necessarily spend much time or money on the ecosystem. I neither played it nor bought a Switch for it, but I did buy Tears of the Kingdom day 1 and played it on sister's Switch.

Core gamers tend to oversell Zelda's impact and undersell Mario Kart's.

It would’ve been nearly identical to what we witnessed with Wii U’s launch, but since the predecessor system was a flop, Nintendo could carry things through with rereleased games. No BotW would’ve left us with Snipperclips, MK8DX, Arms, Splatoon 2, M+R:KB, Pokken DX, SMOdyssey, and Xenoblade 2… all very appealing to core consumers, but this doesn’t come close even to what the NS2 accomplished in its first 6 months, and everybody (well, on Twitter that is) was going rabid over that.

BotW was the reason Switch succeeded. After SMOdyssey, the next blockbuster wasn’t due until December 2018 with Smash Ultimate.

MK is a system seller yes but the issue is that would it have sold the platform as well if BOTW wasn't present as it was the game that generated that initial massive momentum which the other games were able to build on as the thing about MK is that it's a game everyone will eventually get anyway that's why it does such high numbers it occupies a weird spot as a system seller as it's more a complimentary type of system seller.

BOTW bringing in consumers who are outside the typical fanbase is why it's the game that has contributed the most as the Switch platform itself is majority outside of the typical fanbase that's why it's done so well on all fronts and the gaming habits of the userbase differ to the point it impacted third parties on S2 as theses consumers are contributing to the ecosystem. The issue Nintendo had before was their platform's were for the typical fanbase that's why success between their platforms could go from hot to cold and vice versa, BOTW brought in non typical fans on a level only GTA does this is something that's questionable on whether MK would do the same despite doing higher numbers. AC and Pokemon do so although as the context of the topic goes BOTW set the stage for what followed.

You could argue the same thing for MK8 - it sold ~8.5M on WiiU.

BotW (as much as I don't really like it as Zelda fan) as a launch title is exactly what Switch needed - open world romp for "Skyrim generation", that massively expands IP's audience and brings in lot of new fans (just like TES went from 9M to 60M with Skyrim).

But yeah, all combined factors lead to a perfect storm of sorts.