The first three "of the Dead" movies had a very curious premise which was, according to Romero, what would happen if human civilization was replaced. What happens if we're selected against? Keeping with that concept, the "humans" get less and less important with each film. In the first flick, humans fight to survive as a species and all the great race, class, and other stuff comes into play. The second flick, Dawn, takes place after the collapse – all the normal narrative drives for human interaction vanish. There are no classes anymore, there's no progress, race becomes irrelevant because the number of survivors can be counted on your fingers. The second film is weird in that it takes place in a narrative world were the point of narrative – forward motion – is impossible. Day is the most nihilistic in that humans live in tunnels like vermin. They are no longer the dominant species and all the regular characterization tricks are beside the point because they are now in the position the zombies were in the first film – a creepy but manageable threat to the dominant species.

Land, in my opinion, blows it. It swaps this bizarre and novel premise for a fairly heavy-handed attack on current political trends. The next film, Diary of the Dead, breaks continuity entirely and is simply a cash in on the "of Dead" titles. It might be good, but it isn't really "in the series."

I think Romero is in a situation where he doesn't really give a shit about the series anymore, but that's what people will give him money to do. Though I think this started with Land, not Day.