Now this is an interesting discussion to have! Note I have no intention of turning this into a list war or anything, but just to show where I stand on Mario level design, my ranking of the top 10 Mario games is: Super Mario Galaxy 2 > Super Mario 3D World > New Super Mario Bros U > New Super Mario Bros Wii > Super Mario Bros 3 > Super Mario Galaxy > Super Mario World > Super Mario Odyssey > Super Mario 64 > Super Mario Bros Lost Levels. As you can probably guess, I tend to prefer more linear, course based Mario games!
Also, apologies for the long post and rambling, I'm very passionate about Mario platformers and their level design!
Yeah, I can see how someone can get that feeling. Much as I adore NSMBU (and to a slightly lesser extent, New Super Mario Bros Wii), they are fairly ridgid in their level design philosophy, though I feel like this also give them the pro of having rather consistent level design compared to other 2D Marios.
For example, for Super Mario Bros 3 (which is incidently my 3rd favorite 2D Mario and my 5th favorite game of all time, so I still love it!), I do agree that this game shows that you don't ACTUALLY need that level design formula to succeed with Mario level design, as Super Mario Bros 3 stages tend to be very short and focus on only a few concepts without expanding on them all to much. However, this does come at the cost of some consistency in my opinion, as there are levels like the 3-fortress maze and the World 6 "fly with the koopa shell to win" level that don't really hold up that well on repeated plays.
While I agree that Super Mario World's map design and gameplay quirks are really cool, I tend to rate Mario games on more of a level design level than anything else, so I find Super Mario World to be in a somewhat odd position. While Super Mario World certainly doesn't have BAD level design by any stretch of the imagination (in fact, it's great imo!), it does have one very odd quirk: most levels have a drastic shift in design the moment you change rooms. This is especially prevelant in castles. For example, take Ludwig's castle: the level starts in a narrow path, next room is about outspeeding a falling ceiling to reach a ! block to give yourself more time, and the last room is a fence climb to the boss room. All of these could have been expanded into full levels in their own right, but instead they're sorta glued together. Some players I've talked to find this to be a strength, because SMW can pack quite a bit of variety into one level. However, I feel like because of the shifting level designs, a lot of the level design concepts aren't given much room to grow compared to other Mario games, which is why I rate it a bit lower (granted, like I said earlier, I still think SMW is an incredible game!)
Super Mario Bros and Lost Levels have their own very distinct level design philosophies too! Super Mario Bros is something I have a bit of a hard time explaining in words, but it feels like a lot of the game is built around the momentum in your jumps compared to most Mario games, and introducing new hazards so the game can then remix them in more challenging forms later. There's been dozens of great analyses of say, 1-1 in particular, but now that I think about it, an interesting thing about Super Mario Bros is that it almost takes the modern Mario level design philosphy, and applies them to the entire game as if it was one giant level! Considering SMB's crazy limitations due to not having a mapper chip, I think it makes sense to design the game that way imo, its hard to have a ton of variety with stock NES hardware, so its amazing how well the game holds up today imo!
Lost Levels, as difficult as it is, is sorta similar in that regards, except I love that it expands upon the late game design element of Super Mario Bros where it rewards you for taking risks with a power up, aka a chance to make anotehr mistake. 5-4 in Lost Levels in particular has a really nice, challening mushroom to get that feels rewarding to nail!
Finally, 3D Land and 3D World are interesting points to bring up in my mind. I actually agree with the 3D World take a bit: Super Mario 3D World I feel, does actually nail that level design formula better than New Super Mario Bros U, mostly because Super Mario 3D World tends to have a lot more variety in its overall level design. So for example, take one of my favorite midgame worlds in New Super Mario Bros U: Soda Jungle. I love a lot of Soda Jungle's concepts, it does a LOT with poison water, such as the snake block fortress, or the see-saw level with the great rotating see-saw twist.
3D World goes even further than this level design wise, being chock FULL of well explored one-off concepts like the Mario Kart level, or having dramatically different takes on a specfic concept like say, how World 2 and World 9 approach the Double Cherry. I also have to give hats off to 3D World's final level, which takes a Super Mario Bros 1 like twist of reintroudicng various hazards you've already seen in a brand new context! Much as I adore New Super Mario Bros U's level design, Super Mario 3D World tends to focus on less iteration in its level design. NSMBU for example, feels the need to have say, several levels that take advantage of water, or vines, or lava, etc, with a few times such as the bone coaster (which was in NSMBW) or the P-Switch level being afraid to get out of the norm. Super Mario 3D World basically aproaches most of its level design like the bone coaster or world 9 P-Switch level in NSMBU: Most of its levels are some sort of wild idea that don't come back often!
Super Mario 3D Land is sorta similar in that respects, but my huge issue with it is that a large portion of that game is actually remixed content from earlier in the game, which is unforunate, though what's there is pretty damn good imo, even if the difficulty curve is a bit too gentle for my liking. Also, to finish this post off: I actually like Super Mario Galaxy 2 for similar reasons to 3D World, except that game is even more unrestrainted with how it explores new concepts!
