Do you count bad sequels as part of the series?

[Redalgo]

It's really arbitrary for me I must admit, and boils down to whether I liked the bad films in question.

For example, everything in the Alien, Predator, Jurassic Park, and Jaws franchises after their first respective sequels came out are dead to me. Likewise for the new Star Trek films. The fourth Indiana Jones film came close to being fine with me but the leap it made from featuring mystical and supernatural phenomena to sci-fi aliens was unforgivable. Yet at the same time I accept the ridiculousness of most action, animated, and horror movie sequels, am content with the prequel trilogy for Star Wars, and will probably end up adoring the entirety of The Hobbit trilogy in spite of Jackson taking so many liberties.