So far Nintendo's casual focused games on the Switch have seen modest success, but nothing that can pull Wii and DS numbers. 1-2 Switch pulled a solid 2 million copies sold worldwide, and is a fun game in quick sessions, but the game is too niche to be played in many situations, and has a lot filler content you need to slog through. Nintendo Labo is a neat idea, but it's more aimed at kids, doesn't really have multiplayer, and is a more in-depth and involved product that requires a lot of time and commitment to enjoy, rather than something you can pick up and put down with ease. Creative efforts, sure, but neither of them have quite captured what made those Wii/DS casual games so attractive and special. But Super Mario Party seems to do just that. Recently, the game managed to hit 1.5 million in a few weeks, is on its way to outselling every prior entry in the series (sans 8 and DS) in just a few months, and is the game that single handedly boosted sales of Joy-Con. Super Mario Party looks to be Nintendo's first major casual game success story on the Switch.
There's several possible reasons we can attribute to this. Perhaps it's because it's the first Mario Party to return to the original Board game style, which draws a lot of Nostalgia for Young adults and Millenials. Perhaps it's the fact that you only need another pair of Joy-Con for less than $100 to play with 4-players. Maybe its the novelty of its dual-screen use in Toad's Rec room. Regardless, I think it's the first First-Party casual game on the Switch that really hits it out of the park. It's just the kind of game that's really great for house parties or because this is the Switch, pulling out at a restaurant or cafe with 3 other friends. It's simple, quick, to the point.