For the purpose of this exercise, I am going to refrain from entering the argument of Disney v. Grimm. I am talking in general about the story that is in the broader social conscience.
First round: Snow White. Reason? There is a great contrast of good and evil, and a wonderful conflict that gets to the heart of the human condition: vanity. Plus, it's my daughter's favorite Princess. :)
The Queen epitomizes the conflict of beauty and evil. She is gorgeous, but selfish and envious through and through. Her need for constant gratification and support shows the weakness in her armour: lack of confidence. And it is only when she gives up the one thing she holds dear--beauty--that she is defeated. I would say her conversion to a hag is not a change to another form, but the reflection of her soul becoming apparent in the physical.
Snow White is aptly named--innocence and purity as clean as snow. Her beauty is unmatched, but notice how the storyteller places her in her youngest years, barely of age to marry. How could this metaphor for perfect humanity defeat someone so powerful as her stepmother, the Queen? Only through others' weaknesses does she survive: the hunter's weakness to her beauty (he cannot cut out her heart), the Dwarfs' weakness to her kindness (they shelter her, kill the witch for her, and shelter her again in her deep sleep), the Queen's weakness in hag-form (she can deliver the fatal apple, but not save herself from death), and the Prince's weakness for her beauty (searching for her, unable to resist her in the woods). On her own, she is nothing the modern woman would aspire to be--except for those times when we just want to be taken care of!
Courtesy of National Geographic.
Every good mystery pits a good (protagonist) against an evil (antagonist). The degrees of good and evil are certainly arguable and variable, but the conflict is there.
In Snow White, the good vs. evil is, literally, black and white. Snow White--so pure, named for the clean snow-- vs. the Queen--dark of soul and dressed in black. From this we can judge Snow White a morality tale. One is expected to fall on the side of Snow White, and protect the young and innocent from the immoral ways of the world.
In mystery writing, I don't feel one should be so blatant. The stories I enjoy the least are those where the antagonist is in your face and one-dimensional. While the Queen can be seen with deeper facets, and is certainly an apt villain for a fairytale, I would argue a modern mystery should consider the ways evil can camouflage as good and vice versa.
I also don't believe a good mystery has to have a happy ending, a la Snow White. A resolution of some sort must be written, but there need not be a sunset and a wedding. In fact, it often seems trite when a book ends that way.