Honestly, they're all pretty great, but for the Switch specifically, you're looking at titles like Super Mario Bros. Wonder, Super Mario Maker 2, and New Super Mario Bros. U Deluxe in the 2D space.
There are also several that are well worth checking out via the Nintendo Switch Online catalogue. If you want to dig into exactly which ones are the cream of the crop, then you can check out our list of the Best Super Mario Games Of All Time.