I agree with you and Buzz on this. At least DC and company (mostly his writers not so much DC) sought to create a new twist on the lifted material. There are 36 basic dramatic plots as defined by George Polti in his landmark book on the subject. There's almost always bound to be one of these plots used in any story but it's the original take on the basic plot that makes the material fresh. I realize this isn't news to anyone here.
Curtis did inject some freshness into his various takes on the horror genre (he didn't create Barnabas) throughout his career though his post-DS leading men were invariably dark and craggy-faced like Jonathan Frid.
Here are the 36 basic plots to a dramatic story:
This is condensed from Georges Polti's _The 36 Dramatic Plots_.
Each short plot description starts with the title of the plot
pattern. After a hyphen the main characters to be found in the
plot are given, separated by commas.
Supplication - Persecutor, Suppliant, a Power in Authority
Deliverance - Unfortunates, Threatener, Rescuer
Revenge - Avenger, Criminal
Vengeance by Family upon Family - Avenging Kinsman, Guilty
Kinsman, Relative
Pursuit - Fugitive from Punishment, Pursuer
Victim of Cruelty or Misfortune - Unfortunates, Master or Unlucky
Person
Disaster - Vanquished Power, Victorious Power or Messenger
Revolt - Tyrant, Conspirator(s)
Daring Enterprise - Bold Leader, Goal, Adversary
Abduction - Abductor, Abducted, Guardian
Enigma - Interrogator, Seeker, Problem
Obtaining - Two or more Opposing Parties, Object, maybe an
Arbitrator
Familial Hatred - Two Family Members who hate each other
Familial Rivalry - Preferred Kinsman, Rejected Kinsman, Object
Murderous Adultery - Two Adulterers, the Betrayed
Madness - Madman, Victim
Fatal Imprudence - Imprudent person, Victim o lost ect
Involuntary Crimes of Love - Lover,eloveRevea
Kinsman Kills Unrecognized Kinsman - Killer, Unrecognized Victim,
Revealer
Self Sacrifice for an Ideal - Hero, Ideal, Person or Thing
Sacrificed
Self Sacrifice for Kindred - Hero, Kinsman, Person or Thing
Sacrificed
All Sacrificed for Passion - Lover, Object of Passion, Person or
Thing Sacrificed
Sacrifice of Loved Ones - Hero, Beloved Victim, Need for
Sacrifice
Rivalry Between Superior and Inferior - Superior, Inferior,
Object
Adultery - Deceived Spouse, Two Adulterers
Crimes of Love - Lover, Beloved, theme of Dissolution
Discovery of Dishonor of a Loved One - Discoverer, Guilty One
Obstacles to Love - Two Lovers, Obstacle
An Enemy Loved - Beloved Enemy, Lover, Hater
Ambition - An Ambitious Person, Coveted Thing, Adversary
Conflict with a God - Mortal, Immortal
Mistaken Jealousy - Jealous One, Object of Jealousy, Supposed
Accomplice, Author of Mistake
Faulty Judgement - Mistaken One, Victim of Mistake, Author of
Mistake, Guilty Person
Remorse - Culprit, Victim, Interrogator
Recovery of a Lost One - Seeker, One Found
Loss of Loved Ones - Kinsman Slain, Kinsman Witness, Executioner
You can see all of the above in evidence in all of the DS storylines. Remember, confusion is not a dramatic plot against viewers.
nancy
Sadly, this could be said for our own Mr. Curtis, who repeatedly repeated himself when it came to DS! 
