I haven't found that sort of difficulty. Mario & Donkey Kong (& Punch-Out too)are all reflex-based games that I felt gradually increased the difficulty, until the later levels which might eventually have you pulling your hair out. I thought they were consistently so in the later levels, not just one annoying part of an otherwise easy level.
Mario always did that at a sane pace, then "rewarded" you with a golden path of some sort, ridiculous optional levels that you could play at your own risk. Never did beat all of those on the SNES.
The motion controls...yeah that didn't work out so well. It's sadly amusing that some of the later games (again the aforementioned Punch-Out & Donkey Kong Returns) said to hell with that, just hold the Wiimote sideways and set gaming back 30 years controller-wise.
The Wii is good for simple games that you can play for spurts. It's lousy when it comes to, well, real games - with realism, storytelling, etc. You'll never find an Uncharted-type game that you play to find out what happens next. I could never play 120 hours on a Wii game like I did for Skyrim. But sometimes with the bigger games, I find them lacking the simpler, yet more intense pleasures of the insanity that only a cartoony platformer can hit you with. I think I'll hit up Donkey Kong Returns next.
+1. this is very interesting.