1. Most Satisfying
This is about perfectly executed gestures, but why are these videos so watched, even when they are not that well executed or edited in themselves?
2. Oddly Satisfying
There is something to say that these videos are medically calming perhaps, and reassuring about simple tasks done to a t, such as power washing.
3. Super Satisfying Calligraphy
Calligraphy also gets to people, and again the quality of the video is rudimentary, but what's happening is achieving its own form of perfection.
Slime does very well, even if here it would seem more fun to have your own hands in the slime, but maybe not as the repetition / variety gives the viewer a different sense.
As a more artistic, meta cousin of the fail video is the unsatisfying trend, which adds humor to this genre.