The Friday the 13th Films Parts I-X

Of all the slashers out there, Jason Voorhees has probably been the most trademarked with his signature hockey mask. But the storylines from most of his films are essentially the same. There is very little substance. A warning to all who have not seen all the films: this article contains spoilers.
The routine plot is Jason stalks a bunch of misbehaving teenagers who have accidentally trespassed on his territory. He kills them off one-by-one until only one or two characters remain, typically at least one is female. They are usually able to "kill" Jason, or at least incapacitate him, until the sequel. This is how most of his movies go, the only difference being an occasional change of scenery.

But of course, not all the Friday the 13th films go exactly like this. For example, the first one features Jason's mother Pamela as the killer. She, unlike her son, is very human with no supernatural strength or invincibility. The lone survivor decapitates the vengeful mother.

The next two sequels follow the typical plotline I described earlier. One female is left suffering from severe hysterics or dementia after her ordeal is over.

Friday the 13th: The Final Chapter changes up the formula somewhat by establishing a connection with the next two sequels by featuring the only character to appear in more than one of the films in a relatively significant role, besides Jason himself. That character is Tommy Jarvis. This movie features Tommy as a 12-year-old boy who loves to make masks but whom we later find out is quite disturbed after he brutally murders the hockey mask killer.

The next part (A New Beginning) has Tommy in a half-way house after having been released from years of psychiatric therapy. After the murders mysteriously begin again, in usual Friday the 13th fashion, he and the other characters assume Jason has returned from the dead once again. But this story has a plot twist: the killer turns out to be a copycat. It was a psychotic paramedic who was seeking revenge over the death of his son at the same half-way house Tommy was staying in.
The follow-up film (Jason Lives) again features character Tommy Jarvis in his final appearance in the series. The only substance to this story was Jason was being brought back to life with lightning, giving him superhuman strength and invulnerability. But Tommy once again incapacitates the killer by chaining him to a rock at the bottom of the lake.

Its sequel (The New Blood) had a female character, Tina Shephard, with telekinetic abilities. The plot, except for this aspect, follows the same pattern as the others.
The next chapter (Jason Takes Manhattan) takes place primarily in Manhattan, NY. This, again, was the only difference in the story formula.

Its successor (Jason Goes to Hell) has perhaps the most plotline substance of any of its predecessors. Jason's body is destroyed early in the film, but the coroner eats his heart, putting the killer's soul inside his body. Throughout the film, Voorhees jumps from body to body attempting to be reborn via a blood relative. After he finally succeeds, his niece kills him "for good" by sticking a dagger in his heart.

The final film of the original series before the Freddy Krueger crossover puts Jason in space. It takes place in the distant future but, aside from that, everything is essentially the same.
As you probably realize by now, the Jason Voorhees film series provides little in terms of story substance but the character's mere popularity is what contributed to the length of the series.