Outside their first film: Halloween, Friday the 13th and Nightmare on Elm Street are horrible franchises
All three original films really nailed it and are classics and honestly are rather self contained and stood in no need for sequels. The movies that followed on each franchise were all rather bad with some only raising to the level of mediocre at times. All three franchises were also trying to outdo each other with their respective killers Myers, Jason and Freddy and as a result lost their identity.