RE5 wasn't really zombies to me. They used weapons, they had a lot of health, and they just looked like starving Africans.
Then again I just played the demo.
A zombie is just a dead body that was reanimated. You could also view them as a mindless person, doing the bidding of the one pulling the strings.
I'd say RE5. I loved RE4, and RE5 seems a lot like it. I've also tried Left4Dead and wasn't that impressed.