In the past, third party sales on Nintendo home consoles after the SNES have been a mixed bag. Occasionally you'll get a successful exclusive, but most of the time, Nintendo versions of third party titles either preformed bellow expectations, or outright bombed. The the stereotype was that Nintendo players only buy Nintendo games, specifically speaking, anything Mario, Zelda or Pokemon. But the Nintendo Switch is changing that perception. Third party games are doing well on the console. Switch versions of titles regularly sell close to or on-par with their PlayStation and Xbox Counterparts, and a slew of indie games sold more on Switch than anywhere else. Even as the Nintendo eShop grows with new Switch games, sales show no signs of slowing down. Why the shift? Why does the Switch succeed here, where previous Nintendo consoles such as the Wii U and GameCube failed?
I believe it has to do with market perception and concept value. With the Wii U and GameCube, the general audience saw these consoles as a joke. To them, they were ugly, unappealing, and "Kiddy". Nintendo has always been straddled with a more child-oriented stigma, and while the Wii worked to combat this, it also created it's own stigma of being "Casual". As such, Third parties felt there was no audience for their games on Nintendo home consoles because not only were people not buying them, but the audience for many of their games they felt, just wasn't there. Handhelds were a bit of a different story thanks to Nintendo's market dominance, but this left Nintendo home consoles with a dearth of major third party releases. Switch is the first Nintendo system to actively shake the company's reputation. With it, Nintendo's no longer seen as this lame, dorky company that only makes games for your 8 year old son or little brother, but a company that can excite people of all ages. Casual gamers love it for it's shareable social nature with its two detachable Joy-Con controllers, Kids love it for it's toy-like colors and tactility, and adults and hardcore gamers love because it's a sleek device that let's them play some of their favorite console games on the go. No matter what your age or gaming habits are, the Switch has something that anyone can identify with and like. Thus, anything you throw at the Switch will produce great results.
Another reason is simply concept. With the Wii or Wii U, nobody was going to buy versions of third party games there and suffer with poor performance and visuals, just so they can play with tacked on motion or gamepad gimmicks. But the gimmick of the Switch actually offers a reason to buy titles on it either alongside or over the other versions. On Wii, you had to put up with sub-par PS2 visuals and out-of-place waggle controls because the controller lacked buttons. On Wii U, you had to suffer from poor frame-rates and missing features/DLC because of some unnecessary gamepad shit. On Switch? You can take the damn thing with you, not only that, but Nvidia's Tegra X1 processor allows visuals and gameplay to mimic the other versions as accurately as possible. In the case of multiplayer games, the dual Joy-Con controllers and local wireless allow for easy multiplayer in a variety of titles. Everything about the Switch hardware is so compelling and unique, it makes you want to play more games on it.
Now of course, Switch obviously isn't getting every AAA third party title, it's still a tablet with clear limitations. But it's still a powerful, well designed piece of kit that speaks not just to Nintendo fans, but to the gaming audience as a whole. And that's why third party games are doing so well on it.