There are a lot of movies that are remakes that are virtually forgotten. A lot of the originals are silent filmsThe Maltese Falcon has already been mentioned. I’ll add:
The Brass Bottle – the original a “lost” silent film, the remake with Tony Randall, Burl Ives, and – NOT as the genie – Barbara Eden.
20,000 Leagues Under the Sea – there were actually several silent versions, but the best was made just under a century ago, and was filmed underwater (in very advanced technology) in the same waters that Disney would film the remake in in 1954
Thirteen Ghosts – the original was a William Castle “gimmick” film. The remake had a wholly different plot, and was probably appreciated by more people.
She – H. Rider Haggard’s classic was filmed twice as a silent movie before Merian C. Cooper, fresh from King Kong, made the definitive version. It was remade twice after him, once with Christopher Lee and Ursula Andress.
Ben Hur – both the original and the remake were impressive fiolms.
The Ten Commandments – Cecil B. deMille “remade” his own film, tossing out the modern second plot and expanding the Biblical section to its own epic length. The original featured a Technicolor segment (so did Ben Hur) and some state-of-the-art special effects, climaxing with the Parting of the Red Sea. The 1956 remake upped the ante on the effects, again hitting its climax with the Red Sea scene.
The Hunchback of Notre Dame – remade many times, but the Lon Chaney version and the Charles Laughton version both can stand on their own.
King Kong – I know there are folks on this Board who hate Jackson’s remake, but I love it almost as much as the 1933 original. We’ll ignore what happened in 1976.
The Fly – the original is actually a good flick, and generally faithful to Langelaan’s original story. The Cronenberg remake is a entirely different creature (so to speak), and a worthy film in its own right.