Excuse me while I get back to the topic, guys 
Daltrey - very nice! Good analysis with the spacial axis. There's lots of things I agree with. Some (constructive I hope) criticism:
- the axe throwers aren't the only enemies that attack from more than one side at once, yet only they are the "bad guys" of mario's design you mention - since the same element exists in case of flying turtles and axe throwers and only axe throwers are challenging for you, then maybe this element isn't the reason behind it?
- Extra Credits has been mentioned a few times before and I too think it's a good reference. One thing you can see there is the length of the video. No matter how interesting it is, 16 minutes is a commitment not everyone might want to make. Especially since you get back to the same elements and repeat similar conclusions (like growing and yoshi) that could have been placed together and described in a faster, more efficient way.
- saying things in the end of a video that "there are hundreds of elements that build this game's depth, but we don't have time for that" makes the viewer wanna say "name ten more." And it's not a challenge - sentences like this just never sound good. They sound either ignorant or indicate that the author pretends to know more than he actually does, so why risk leaving this kind of impression?
All in all, I repeat - nice work and nice example how the game design can be analyzed.
Good luck in future videos!