There had been zombies in movies well before Night of the Living Dead, but this was the first "zombie apocalypse" movie. It is the thoughtful tone of the movie and the convincing actions of the characters that set it apart from the others. Many have said that Night of the Living Dead was the first modern horror film. It is intelligent, but also, in places, quite nasty, with scenes of gore and cannibalism.
Hardcore horror movie fans today will not be shocked by it (it is relatively tame by modern standards), but if you are the sort of person who feels squeamish at the meat counter of a supermarket, you should probably give this one a miss.
Michael Jackson and Simon Pegg have done their best over the years to make zombies seem ridiculous, but despite their efforts, Night of the Living Dead is still a chilling and thoroughly convincing horror masterpiece.