1. SMM. The SMB mode's physics don't match the original game, no slopes (among other things of that sort), no SMB3 suits, and the whole thing feels cheaply made at times.
2. NSMBU. It's Wii HD with a pretty meh new powerup, and Wii wasn't a great game to begin with.
3. NSLU. Why would you make awful DLC for an already awful game?
4. NSMB2. It feels so cheap in quality, Star Coins are hidden in cheap ways often times, and lacks really anything of a difficulty.
5. 3D World and 3D Land. Unlike the 2D games, neither feels exactly cheaply made, but they both continue to lack difficulty. Mario games need to stop being made so family-friendly in these areas, and make them actually challenging again. This is why the great majority of games I play are retro. The post on page 1 of this topic criticizing SMB2J is wrong, the game has more to it than that. It's not like NSLU where the levels weren't improved, SMB2J's levels are much more expanded and complex, and it really adds a lot to the game. The same hasn't been able to be said for years now. Looks like Odyssey might finally break this pattern, though.
6. SMA4 e-Reader localization, or rather the lack of it. Not satisfied with the VC release, I went out and tracked out the majority of the Japanese cards. In the VC release the Switch Cards are still not accessible, neither is the blue boomerang, and it's not the e-Reader experience. I have all seven Switch Cards, and am missing eleven out of thirty-eight (nine main levels, one classic level, and one promo). I am still missing some of the best, e.g. A Sky-high Adventure (a.k.a. Inner Maze on an older patch or as it translates to, The Secret of Tanooki Mario), but it's still better than the VC release. There's nothing like breaking Castle Dash/60 Seconds/Run the Tower with the Green Switch, testing out which enemies can be killed with the blue boomerang, or even just the satisfaction of scanning the cards in themselves rather than having all the levels handed to you immediately. They're experiences that can only be experienced the legit hard way or printing out the dot codes if you have a good enough printer. I was the one who added all the difficulties to the Wiki, because it's just so hard to do things legit, and it's a shame. Next 2D Mario game should do something like this in all regions, and like SMA4, have challenging, complex levels. We've seen that it's possible through the Animal Crossing amiibo cards. It just needs to be re-purposed for this.