That's a criticism you can also lay at New Super Mario Bros. U's door. While it's also an excellent 2D platformer, and one of the best of its kind on Wii U, it's still a bit by the numbers and didn't really do enough to distinguish itself from the Wii or DS entries.
Much like the 3DS's 3D visuals didn't transcend that experience, the move to HD didn't really do much for New Super Mario Bros. U.
6 Golden Coins is a direct sequel to Super Mario Land, but improved on it in pretty much every area. The visuals in particular saw a sizeable boost in sophistication, with the style similar to Super Mario World on the SNES. In fact, it also included an overworld map and allowed you to move left and right in a stage.
It also made a welcome return to the Mushroom Kingdom and introduced the infamous Wario as Mario's foil. Oh, and it includes way more levels than the original, which was really the only complaint of that one. Basically, it's better in all ways. Just accept it and move on.
The New Super Mario Bros. trend might feel a little tired at this point, but back when it launched it felt really fresh. This kickstarted the 'New' formula, and revived the 2D gameplay in glorious 3D.
Though all of these games pretty much feel the same at this point, the game that started it all deserves its high place in the list for creating a whole new way to experience classic Mario.
Next up is the game that started it all – Super Mario Bros. on the NES. Such was its popularity that it remains to this day the sixth best selling video game of all time, and the highest selling Mario game. That's incredible, given the fact it launched way back in 1985.
Even more impressive than that feat is how well it's aged. It's still an awful lot of fun to play even today, with excellent controls, level design, and mechanics. It's incredible that Nintendo nailed the formula in the very first entry, and that both 2D Marios and other 2D platformers still largely follow it.
Super Mario 3D Land is an interesting one. Mario creator Shigeru Miyamoto describes it as a 3D Mario that plays like a 2D Mario, and we can't really argue with that.
The levels are fully 3D, with Mario able to move back and forth along a 3D plane, but the view is more often than not side on. It's an impressive feature, made only the more so thanks to the excellent 3D effect of the 3DS.
Visually, it bears a lot of resemblance to Super Mario 3D World, which later launched on the Wii U. Simultaneously gorgeous, fresh, and an excellent example of a Mario platformer.