Dracula:
DRACULA(1931)***1/2
NOSFERATU(1922)***1/2
DRACULA(1979)***
HORROR OF DRACULA(1958)***
DRACULA(1931-Spanish)***
COUNT DRACULA(1977, Louis Jourdan)***(I haven't seen this one in awhile, I might rate it higher if I had a fresh look)
NOSFERATU THE VAMPIRE(1979)***
DRACULA(1973-Jack Palance)**1/2
BRAM STOKER'S DRACULA(1992)**1/2

Frankenstein
BRIDE OF FRANKENSTEIN(1935)****
FRANKENSTEIN(1931)****
YOUNG FRANKENSTEIN(1973)****
FRANKENSTEIN(1910)***
THE CURSE OF FRANKENSTEIN(1956)**1/2
FRANKENSTEIN:THE TRUE STORY(1973)**1/2
MARY SHELLEY'S FRANKENSTEIN(1994)**1/2

I included BRIDE in the ranking because the film does credit itself as being based on Shelley's work. Also, some of the situations are more faithful to the original story than the 1931 version.