What was the best movie that had the worst remake?

Hollywood has a bad habit of trying to remake remarkable films. La Femme Nikita was terrific, but the American version sucked big time. The original The Day The Earth Stood Still is one of the best ever, and the Keanu Reeves version fell far short. I see they are remaking Robocop now…
So, what original movie and its remake had the largest quality gap between them? I have two suggestions, which I will hold back for a bit, to see if they are mentioned by anyone else.