I like all zombies. If I had to pick a favorite I'd pick the Romero zombies. I wish someone would make a zombie RPG with Romero zombies. I don't care much about the zombie origin story...dead rising, infection, whatever. I figure zombies don't attack each other, they can travel in packs, and they possess no more strength than what the host is capable of.
Here's how I see it though.There are really 2 main genres in the world of zombies.
1) There's the Romero zombies that are slow and mindless; these are the zombies in Shaun of the Dead and the popular comic The Walking Dead.
2) Then you have the "fast" zombies.
3) Other (which I'll discuss in brief, but this is like "Return of the Living Dead")
Let's start with 1). It is my opinion that the "Romero" zombie is more of a vehicle to study human nature. These zombies are slow and stupid and do not pose an immediate threat, especially in small numbers. Therefore human survival is very likely. This allows the author to set up a situation where humans are trying to survive in a post-Apocalyptic environment. Usually this results in a fairly cynical outlook on human nature. Romero's genius is that he is able to not only use zombies as a vehicle to study human nature but he ALSO makes movies that are pretty scary. As Prof S noted, in Romero's films there is a theme of inevitability, a slow and drudging realization of impending doom. A notion that you cannot escape and you will become a zombie. There are themes of despair. And lots of gore to boot! On top of looking at human nature and scaring you, Romero also decided to make Dawn of the Dead a social commentary. You know...slow, mindless zombies...walking in a mall. What a mockery of consumerism! Yay!
2) Fast zombies. The infected. Etc. I feel like the fast zombies are immediately more frightening. But as we saw in 28 Days/Weeks Later, humans don't really stand a chance against these fast zombies. I love the 28 series and I look forward to the release of 28 Months Later. I think you can combine fast zombies and a wonderful post-Apocalyptic survival story. I thoroughly enjoyed Zach Snyder's 'revision' of Dawn of the Dead that came out in 2004.
3) Other is the mesh of the monster genre with the zombie genre, or the parody takes at the zombie genre. I'd probably dump the Resident Evil Trilogy into here too. There's not much to say here except, "BRRRRRRRRRAAAAAAAIIIIIINNNNNNNSSS!"
Finally, my favorite scene from Kill Bill Vol. 2 is the part when Uma gets buried alive. I always wondered if Tarantino is a Fulci fan. I have great respect for horror filmmaker Lucio Fulci. In his 1980 film, City of the Living Dead he brings us this AMAZING scene:
Seriously, is this not one of the scariest scenes from a movie, ever? The build up is fantastic...and the view from inside the coffin. And the way the axe almost hits her. Oh man. Brilliant film making!
Here's a longer clip but there's music over it ruining the magic: