The entire second half of Quick Man's stage is totally unfair first time through. If you don't land where the game wants you to land, it's death.
I can't comment on MM5 since 4-6 are a blur in my head. As for Quick Man, evil yes, but doable. At least in that case you can see obstacles as they scroll up. Placing a wide death trap at the bottom of the screen, invisible until the instant before you fall, is another story. And again, where you fall is luck-of-the-draw, so that's at least SOME chance, which is not the same thing as fixing you where you're screwed if you don't know what's coming, which is what Splash Woman does.
Most such hazardous falls in classic-series also include lots of spikes in the scenery beforehand, effectively warning you to keep your guard up. The worst fall that I recall in classic-series is Doc Robot Spark Man in MM3, and even that's not so bad if you stay calm.
It's not that MM9 is hard, in fact it's actually quite easy, it's just that it makes the habit of blind-siding you. Lousy design in my book, not that I don't like the game overall. I do. But I don't think it holds a candle to a true NES game without factoring in Endless Attack and ProtoMan Mode. Even then, 2 and 3 are still superior.
and Mario Kart.
Depends on which Mario Kart. Double Dash is dirt-simple. Wii, on the other hand, is utter lunacy on 150cc.
But you know, I might have even put up with that if a FREAKING PERFECT SCORE was enough to satisfy the unlock conditions. But it wasn't. A full F*@#!ing 60 points, which in itself took many replays, and I get a measly B rank. At that point I consider myself fully justified to hack a constant Star Man and blow through those bastards (hey, I wanted my Dry Bowser).
Also on DeviantArt, Rumble, DLive.tv, and the Fediverse (@freespeechextremist.com and @bae.st)