I disagree, to an extent, about the "soul" bit. I'd have to say, if anything, it's that in some worlds, the theme is underused, and that because of this, some individual stages come across as unmemorable. It's a great game, but to really get the best feeling from it, it has to be played with at least two players. Once you experience the game in multiplayer, it really takes on a life of it's own, that doesn't really compare to other Mario Bros. experiences in a way most of us are familiar with.
I'm glad it doesn't have online, because this is exactly the type of game online play can literally rip the soul out of. I'll say that.