I think NSMB multiplayer is enjoyable if you're specifically playing it just for the fun of not caring whether/when you get through it.
If you are trying to play co-op with intent on getting 100% and plowing through levels, you're doing it wrong. You need to play it as casually as possible and playing it for what games are meant for, fun.
But as a completionist, and someone that likes having a perfect file, you're going to want to play on your own first, probably.
Personally, I liked the Versus mode in NSMB1 and I felt like the multiplayer modes in NSMBW were kind of useless (the alternate ones).
This is why I liked Four Swords more, since it not only accommodated to the player count, and had random layouts (the original anyway), but the game knew it was competitive AND co-operative and blended them properly. You got rewarded for being a better player and beating your friends, but you worked together and NEEDED your friends to progress. I enjoyed that.
Similarly, I enjoy the multiplayer for Luigi's Mansion a lot. But I think Rush/the time one is a little unfair in any instance other than with 4 players. It's doable with one or two, but it's extremely hard due to having to cover so much ground in a short time and often maps that wind around and make it impossible to get back if a friend finds the exit on another end of the mansion, even with timers.
Mewtwo, ZSS, Ganon, Ice Climbers, PT, Ness/Lucas, Shulk, Isaac, Saki, Tingle, Takamaru, K.Rool/Dixie, Belmont, Pac Man.
Olimar, T.Link, Zelda, Little Mac~ Backloggery ~ // ~ Tumblr ~