The big mystery is how and why did people flock to this movie above other late '70s/early '80s horror movies and make it the Sequelizer That Wouldn't Die? America, you brought this monster upon yourself.
33 years after its release I finally made my first trek to Crystal Lake, although I have seen parts of a couple of the terrible sequels. What first strikes me in 2013 is how *slowly* it moves! There are times I nodded off while watching young camp counselors attach the pier, cook some food, and clean the gutters. Only the direct Psycho-ripoff violin cues reminded me something scary was supposed to happen. The scare setups are clumsy and often ineffectual - make no mistake, this is just another low-budget ho-hum horror that happened to get lucky at the box office. Also surprising, given its reputation, is the lack of blood & gore with several kills offscreen. Texas Chainsaw Massacre carries a similar reputation, but it features suffocating atmosphere and creepy characters to generate horror, thereby multiplying the potency of the existing violence. Friday the 13th doesn't have any of that, and consequently is as frightening as a squeaky screen door.
It does boast one enduring claim to proper fame however: Kevin Bacon! Yes, Kevin Bacon is in this movie, he's been in close to 600 of them but here he is still a rookie in his 4th feature. As a bonus, he is killed off through one of the superior stabby effects shots.
Undeniably influential in popularizing the slasher genre, but I fail to see how it is any better than even the averagest among its shoddy imitators.