Bit disappointed it was only mainstream platformer levels. Some of the ones in the Yoshi spinoffs (Island, Island DS, New Island and Woolly World) were brutal.
As were some of the areas in the Mario RPGs.
Ugh... Grandmaster Galaxy... yeah, that was bad... never beat it either... came close once, but a Hammer Bro nailed me. Actually, I might have put that second to Champions Road, since I never got anywhere in that one.
I think tubular is too high. It wasn't as hard as the final level of 3D World.
Still number 1, those hammer bros. prevent me for winning. >_<
I got more than halfways in Champion's Road. At that time, I did not have the patience to finish, but I will someday!
Point 1: Super Mario Maker's ever-growing list of creators is in the verge of making this list null and void. Moreso if you include creators of unofficial hacks/mod.
Point 2: WHY ARE WE STILL CARING ABOUT WATCHMOJO ANYMORE
Why do people strongly dislike Watchmojo? Their top 10s are usually well researched with a good explanation.
Video quality isn't the issue, at least for me.
As I also stated in the last WM-related story here on GoNintendo, I strongly despise Youtube channels/people like WatchMojo out of a principle: by making the exact same kind of video every time... every day... up to 3-4 times DAILY, WatchMojo goes in violation of one of Youtube's Community Guidelines and STILL racks in the dough without any kind of strike/notifications from Youtube of sorts. Quoting the "Spam, misleading data, and scams" voice in the Community Guidelines' main page (link):
[...] It's not okay to post large amounts of untargeted, unwanted or repetitive content, including comments and private messages.
Sure, WatchMojo's case is going on the softer side of this point in particular, but It's certainly guilty of the repetitive aspect.
I used to find "Outrageous" in Super Mario World to be the hardest of that game. Not "Tubular". I can beat Tubular fairly easily, once you know what to expect further in, anyone can beat it.
I found the Impossible pack much harder than any other stage on this list (maybe the final stage on Super Mario 3D World is close to it), Tubular to me is kinda of easy, so I'm surprised to see it as a number 2.