It's probably worth noting that the most faithful movie adaptation is not always the best one. The Charles Laughton version of THE HUNCHBACK OF NOTRE DAME completely changes the ending, but works as a classic movie in its own right. Which is often the case.
Speaking of DRACULA, though, the 1970's British version starring Louis Jourdan as the Count is probably the most faithful adaption of the novel I've ever seen--aside from the casting of Jourdan, who plays Dracula as suavely sinister in the manner of Lugosi.
As for JEKYLL & HYDE, pretty much every movie version varies significantly from the novel because (unlike the novel, where it's a surprise ending) they don't try to hide the fact that Jekyll and Hyde are the same person.