I’ll just say a couple sentences about them and if people care then we can talk about them more.

Worst to best

Friday the 13th (original) - rewatch, but I’d only seen it in pieces with commercials before. The use of locations is great and now it works as a period piece, so there’s some charm here. And the girl who dies first seems sweet so I was sorry to see her die. But aside from good location work this is pretty artless and really not scary, except for the very ending, which I admit is pretty great. The only other great kill is Kevin Bacon’s famous death. I assume that it’s popularity depended alot on teens at the time identifying with the characters, and then leaving their small town drive-ins to go park in the woods and makeout and smoke pot and then getting spooked because it felt like they were in a scene from the slasher movie they just watched. Do kids now still watch this and think it’s scary?
I’d say that I enjoyed every movie in this post more than not, but this one is at least 50% bad, and that’s being generous.
Recommended if you’re watching it as a period piece or for historical reasons, but not for much else.

Cult of the Cobra - We have Cat People at home, but do we have SNAKE people at home? This is an okay ’50s horror movie about some soldiers who crash an Indian snake cult like a bunch of asshole Ugly American tourists then go back to America and start getting killed by a mysterious snake lady. I’ve been curious about this one for a while since I saw someone who posts alot on various Western blogs say he likes it. I enjoyed it but it’s not that special, aside from maybe being a 1950s movie that feels more typical of the ’30s or ’40s.
Mildly recommended if you’re a big fan of classic Hollywood horror, but even then it’s far form a must-see.

Katasumi and 4444444444 (1998; short films)
Ju-On: The Curse (2000) & Ju-On: The Curse 2 (2000) - Made for Japanese TV
Ju-On: The Grudge (2002) - Theatrical

The original Japanese Grudge movies, which started out as shorts/direct to video. Something something J-horror ghosts, something something. I watched these in the last two weeks and they’re already a big mush in my mind. Great direction and good scares, but they’re repetitious as hell and I couldn’t tell you a thing about the plot. The TV movies are on youtube and are basically one movie, with the second one starting with 30 minutes of the end of the first one.

Maybe just go straight to the original theatrical movie and then go back to the earlier ones if you love them. There’s nothing that can be meaningfully spoiled.
Yeah, I’ll say the theatrically released Ju-On: The Grudge is recommended but not essential, and then earlier releases are recommended if you loved that one.

I think I’ll skip the sequels, but I’ll probably watch the first American one, even if you wall tell me it sucks.

I usually hate to dismiss stuff just because similar movies are better, but Ringu is similar and has a plot and crushes this.

Pumpkinhead - Directed by Special Effects giant Stan Winston. Spoiled early-20 somethings from the city run afoul of country folk and are cursed to be hunted by a monster. This is the most bog-standard of plots, but it looks great and has fantastic monster effects. Must-see for fans of old practical effects. There’s not alot else to talk about though.

Drag Me To Hell - Another movie that makes me feel old because I meant to see it in the theater and am not only getting around to it 17 years later. Sam Rami returns to his roots in this 1980s style horror comedy about a G[offensive term for Romani people] woman who puts a curse on a young woman who wouldn’t extend her mortgage. I watched this and Cult of the Cobra the same night, not knowing that either was about a Lamia, and they both were!
I thought this might feel tame and compromised because it’s PG-13, but it’s pretty gross. IMHO, it’s an absolute blast (with one huge caveat that I’ll get to in a moment), and does a great job juggling traditional suspense, psychologically anxiety, and gross-out-splatter-humor.
My big caveat is that a throwback 1980s pop-horror movie like this just begs for Tom Savini/Wes Craven-style practical effects, but what we get is mediocre CGI. I realize that that was probably the only option, because the infrastructure was no longer there and it would cost too much to pull together that type of production in 2009.