Ok I gotta speak up on this point. The Dawn of the Dead remake and 28 days and weeks are NOT zombie movies! Romero calls them "infected" movies. Sure their good (well Dawn was really only good for the first 20 minutes or so) but theres no creepiness with the infected. 28 Days and Weeks Later were good and scary movies but the speed of infection and behavior of the infected was unrealistic. Although I admit I would probably lose control of my bowels if I encountered a rage-infected person.
Now, seeing as how George A. Romero CREATED undead zombies, I'd say his Dead movies are the best. Dawn and Day were the best in the Dead series. They are absolutely must see movies. The social commentary in them was eye-opening for me. In a world where zombies outnumber people, you better beware of the people... The zombie effects were absolutely fantastic in Land of the Dead (probably the best of any zombie movie) Diary of the Dead was great too. Its like a zombie documentary. And his new movie Survival of the Dead is a great story. Oh and the remake of Night of the Living Dead (the original was the first zombie movie ever) was incredible. And I mean the remake Romero did himself in 1990, not the crappy 2006 remake.
Now onto non-Romero movies. Shaun of the Dead is amazing. It was a hillarious and smart movie. Its my favorite zombie comedy. I LOVE the scene where Shaun walks to the store in the morning after everyone starts to wake from the dead. He slips through puddles of blood and encounters a zombie beggar and still remains oblivious! As I said, hillarious! Zombieland falls into that category too and even though the zombies are similar to those in the Dawn remake, I'd still say its a good ZomCom.
And finally on to Resident Evil movies. I'm not even gonna call those live-action discraces zombie movies. The zombies in them were good (at least in the original and Apocalypse) but they are not horror movies they are action movies. BUT, Degeneration was great! Even though the zombies were only in the first half hour or so of the movie, it still had some great scenes, and I say that not as a Resident Evil fan but as a zombie fan. Leon throwing Claire the handgun in slow motion, MINDBLOWING! Dat chick's got mad skillz!