Looking at that chart of the Switch's 10 best selling games, I think there's a conversation to be had about NSMB, perhaps even 2D platformers in general. In a vacuum the sales are great, but it isn't experiencing Switch growth like other IP.
It's the lowest performing NSMB game except for the original NSMBU, and even then it's hard not to find the original's results more impressive given the install base it had to work with on Wii U.
i would like to meet the person that looks at NSMBU and says "I'm really excited to play this game." I just don't think the star power is there for new NSMB games, especially since they've all used a virtually identical setup since the Wii game, with the same 8 worlds and the Koopalings, and even the "giant Bowser" boss fight at the end.
Before NSMB, every Mario had a really unique set of gameplay hooks, settings, and characters that made the games feel more grand and more uniquely Mario.
Super Mario Bros. 2 USA obviously added a ton of iconic characters and elements, like the unique character attributes, the Shy Guys, Birdo, the new Subcon setting and its biomes & unique music.
Mario 3 obviously added a bunch of shit, including the iconic airships, Toad Houses, the Raccoon/Tanooki/Frog suits, the concept of mid-world Fortresses, the Goomba's Shoe, an explorable world map, the Koopalings, new block types, and two players going co-op through the same adventure.
Mario World was also radically different even from 3. It had the Cape+Yoshis, secret level exits, a single world map with passages between worlds, new biome types (Choco Mountain + Forest of Illusion + Star Road), and again a whole bew
With NSMB DS, the big hook was that it was the first all-new 2D Mario in 15 years (debatably less if you count Yoshi's Island). It built mostly on established ideas, but it did add a few never-before-seen characters.
With NSMB Wii, we mostly got NSMB DS on console, with simultaneous co-op multiplayer added and the return of the Koopalings. We also got the Propeller Suit, Ice Flower, and Penguin Suit, though none of those really achieved iconic status. Really hard to say it had any other significant gameplay hooks or new content (new settings, characters).
NSMB2 had a gameplay hook: coins. But other than that and having an associated score attack mode, I'm not sure what the selling point here was even supposed to be. None of the radically new/different stuff we got from 2/3/World, even though we shifted to a new platform. still very rooted in NSMB Wii. The Raccoon suit came back, though?
NSMBU adds new artwork for the established biomes, brings back the single world map, and introduces the Super Acorn. It also has Nabbit, I guess? But otherwise it's barely distinguished from NSMB Wii. Same structure overall, same content ideas reused, same gameplay mechanics across the board.
2D Mario hasn't had a big selling hook since NSMB Wii's simultaneous co-op besides "so I herd you liek Mario Bros. games" and it shows in the sales.
Despite this, there's clearly a hunger for Super Mario Bros. games since they still sell millions of copies. And people love the new shit in Mario Maker, but I think that game being based on user-generated content hamstrings its potential; people want a grand Mario adventure like the ones they got with Galaxy and Odyssey, but in 2D.