Well, thanks to isohunt tricking me, I have just watched the remake, and not the original, of Night of the Living Dead. This means that I can't say all that I would like to say about the movie and the impact that it made, since wikipedia has kindly informed me that the two scripts are not identical (and are they ever?)
Social commentary aside, I can see why this is cited as the zombie movie of the modern era. Regardless of how it changed the definition of how we think of zombies, it is amazing at taking the mythology about zombies and why they're scary, and getting to the core of it.
There's been a lot of changes to the zombie genre, changes designed to improve upon a tired, classic idea. There have been running zombies, smart zombies, zombies with unnaturally long tongues, zombies with guns so on and so forth. This movie takes the whole thing back to formula. It is about people, in a house, surrounded by zombies. And that's it. While I was watching it, I realized that the whole thing could potentially work as a play, because the setting rarely changes, which is definitely not a bad thing in this case.
When your movie is nothing but a house, some people and zombies, the plot is accelerated by the people, since houses don't do anything and zombies really don't do much more that. I think I can state the claim that this movie isn't about zombies so much as it is about a group of panicked and scared individuals...who happened to be attacked by zombies from time to time. There should be more movies like this, that focus on the bare bones of the thing instead of putting a machine gun on their monster or whatever dumb shit Resident Evil is up to these days.