Ive seen pretty many of them but i guess ... the best is "28 days later" and "28 years later" ... fast action, running zombies - not those slow ones in the resident evil series
In 28 Days later they haven't died. They are living humans with an infection that makes them extremely aggressive, more akin to rabid dogs.
Definition of Zombie is the "living dead" ie they must be dead. In 28 Days later they are not dead, just infected. Eventually they starve to death and die and no longer walk around attacking people. QED they are not Zombies.
In Resident evil, they were killed by an infection but attacked people whilst dead. QED they are Zombies.
Non of these films are based on a real issue, so debating what they are and what they are not is just really pathetic. But by the look of your avatar, you probobly speak klingon.
Me and my friend got Shaun of the dead now (i didn't watch it yet) We will click play at the same time like we have done on many other movies. We call it movie nigth. It's not gay though, balls aren't touching.
All zombies come from some sort of Virus or Infection that re-animates them and brings them back to life with basic functions, Which is Hunting, And Food.