Your experience may very well be limited in scope, it's not a justification for saying SMS has potential.
I don't think you understand the underlying problem here. SMS, at its core, is about having a ridiculously overpowered character that trivializes every aspect of the game. This is boring. It is absurdly bad design to take everything that makes the game fun and interesting, and make all of it completely irrelevant. This is completely counter to good character and game design. When something's design is completely counter to the purpose of the thing it's being made for, that is, by definition, bad, unsalvageable design. It's irredeemable because it is not congruent with the game's design, and completely counters all of it. And this is before getting into the nitty grittys of the shit quality of the sprites.
Nobody is saying you can't have fun with SMS, but that fun is entirely subjective. It is not based on any metric you can use to assess good design. Lots of people fun playing with things they know are awful. But many of those people will tell you that they're aware of how awful what they're doing is and won't justify it. SMS definitely fits in the category of "Something people can have fun with but has no objective merit". This is not pessimism. This is an analysis of the material presented to us.
It's something to do while listening to the soundtrack, of course =P