I spit on your grave was slightly better

"As for the characters in the original LHOTL, I felt no sympathy for Mari or Phylis whatsoever."

Why is that? There's plenty of character building in the first act. In fact, I find their characters and the dichotomy of their friendship to be fascinating, thoughtfully developed and, frankly, rather sweet.

For example, Mari telling Phyllis that she would like to "make it" with Bloodlust in a bunch of cotton, and Phyllis's reaction ("It's Bloodlust, man, like they're crazy!") is not only amusing dialogue, it serves to establish the contrast between Mari's naivety and Phyllis' comparatively mature worldview.

I personally find it interesting that Phyllis appears to be on the verge of world-weariness, having endured a youth in the slums of the city, and is drawn to Mari's childlike innocence as a means by which to vicariously see the world anew through the eyes of someone who hasn't witnessed the horrors of humanity.

In turn, Mari is drawn to Phyllis because she is eager to become a full-fledged woman and views the slightly older Phyllis as a sort of mentor; the dialogue in which Mari revels in the fact that her breasts had filled out that summer informs us that she is on the teetering point between adolescence and adulthood, and is ready to embark on such endeavors as sexual experimentation and drug use... but we are reminded that she is still the emotionally underdeveloped girl celebrating her sweet sixteen when she enthusiastically sings: "Rodney Johnson!" It's clear during these scenes that Phyllis enjoys being in the company of Mari and her gleeful, untainted youthfulness, which Phyllis appears to have missed out on entirely.

LAST HOUSE ON THE LEFT is a shockingly well-written movie, especially where the characters of Mari and Phyllis are concerned. Granted, Craven was fully aware that he was making a low budget horror film, so he knew he had to give us as much character development as possible in a very short time so as to not bore his target audience (teenage drive-in patrons). I feel he achieved that, and expertly so, but because the construct of his narrative moves at such a necessarily brisk pace it does require the viewer to be focused on details and desiring of extreme emotional impact.

In summing up, this is a serious attempt by an intellectual novice filmmaker to make a complex and thoughtful yet marketable and broadly palatable micro-budget thriller-cum-cautionary tale for freedom-seeking youths in the post-'Nam/Manson era. Craven admitted to have grown up in a violence-laden urban environment and was no stranger to acts of violent aggression, and it shows in this movie. It's the work of someone who understood - and was deeply fascinated by - the psychology of people who enjoy perpetrating acts of violence and cruelty. As a meditation on violence and sadism, it poses a great many questions to the viewer, one of which is: How big a divide is there between those who commit violent acts for no good reason and those who commit them for what they feel are very good reasons?

It's an absolute masterpiece, warts and all.