Both Mary Shelly's Frankenstein and Young Frankenstein were both great movies, though, I preferred Mary Shelly's Frankenstein a little bit more. I"m not really into those old comedies. Anyway that is not the point the point is that both movies no matter how different they seemed to be, were derived from the same original horror story written by Mary Shelly. The movies may have small similarities and that is because they both still come from Shelly's original story.
Mary Shelly's Frakenstein (the movie) has a strong basis upon the original story. Shelly wrote a horror story it continued as horror movie.
The movie is set in Geneva Switzerland in the 19th century (I think) and in a place called Ingolstad. The movie revolves around Victor Frankenstein, son of a wealthy Swiss doctor and a kid that saw everyone he ever loved die. He watches his mother die giving birth to his brother, there he vows not to see anyone else die again. He moves to Ingolstad to study medicine, leaving behind his wife to be telling her he will return. While in school he becomes fascinated in the reanimation of dead tissue. His professor was the closest to reanimating dead tissue but he stopped his work because it wasn't right. Victor pleads with his professor to no luck, until a patient kills his professor. Victor takes his notes and creates the monster. The monster escapes with the journal and eventually learns to read and tracks down Frankenstein to demand he make him a wife. Frankenstein does not go along and the monster says he will be there on Frankenstein's wedding night. The monster kills Frankenstein's wife and victor races back to the house to try to "fix" her. Once figuring out what has happened to her she commits suicide. Victor follows the monster to the North Pole to kill him where they both perish.
On the other end of the spectrum lies Young Frankenstein a comedic twist on the Frankenstein story by Mel Brooks.