I was thinking with all the different horror movie franchises most of them rarely have more than a couple good ones. The first one is almost always the best, a classic or great movie. The 2nd one is usually the next best but inferior to the first and then they churn out worse films until sometimes will put one out a later one that brings back the spirit of the first movie but still doesn't match it.

What are your favorite horror movie series and are there any that don't follow this pattern?