You might not need "Super Skills" to play New Super Mario Bros. Wii, but as this video shows, it certainly wouldn't hurt.
It's a NSMB Wii trailer two-fer!
Now, I don't know that I'm seeing any of this supposed Contra-esque difficulty in the above videos, but what I am seeing is a variety of powerups, and the use of said powerups to get lots and lots of 1UPs. Whether you think that the whole concept of "extra lives" is irrelevant in modern gaming, those are indeed, some clever Super Mario tricks.
I'm actually a lot more interested in the various powerups the video shows off. We see the standard Star and Fire Flower that have become staples of the Super Mario franchise, but also three new-ish abilities: A penguin suit that lets Mario slide across ice, a propeller-head suit that lets him glide, and a frozen counterpart to the Fire Flower.
This last one is intriguing: We all knew Mario was a psychopath that had no problem stomping on various animals like turtles to slaughter them, but somehow it feels a bit more visceral when he freezes an enemy in a block of ice and then dashes it against the side of a cliff, shattering them into tiny pieces. Mario, you fiend!
(Okay, the penguin suit looks pretty fun. I have to admit that)