The Dark Knight is overrated,but it's far from a mess.It is perhaps too long and maybe even takes itself too serious - too cold and cynical? I personally felt that the length and seriousness added to the movie,but did find the ending slightly confusing.
There are still more than enough great things about it.
I'd say A Nightmare on Elm Street is overrated.It's highly imaginative,with a great and genuinely scary villain.It's the misguided 4th quarter of the movie that takes away much of the film's impact.
Halloween is another one.It's a triumph for cinematography,acting and as a basic chiller/thiller.However,the plot is extremely thin,and without much in the way of characterization.There are also a number of goofs.