28 Days Later is by far the most realistic and conceivable 'zombie' film ever made and for many reasons, it is also original and changes your perception of it happening.
How many times have you heard someone say 'Oh, i'd love a zombie outbreak like Dawn of the Dead so I could go to a shopping mall or bash some zombies in gamer style' i'm guessing alot? Well how many times have you ever heard 'i'd love to be in the 28 Days Later universe'? Yeah, never.
It's fucked up and depressing, parents ripping their children's faces off, the infected aren't hungry for brains they want to pull your tongue out and cough blond into your eyes so you then turn into a rage infested animal and want to rip someone else's face off.
They also got the tone perfect, a grey, dark feel that when watching you felt there was no happy ending or silver lining, everything was fucked and just being there would make you wanna hide under a bed forever because these things don't claw at glass windows like normal zombies they chew threw the thing to get you, they will tear walls down and rip doors of hinges if they know you are inside, there is NO escape and they are relentless.
For me the film fell flat at the end, I find it stupid that army soldiers living in a post apocalyptic Britain would be so quick to want to rape any women they come in contact with especially one being about 13, it kinda lost me there like come on? Really? Everyone you know and love is dead but you are to horny to care. It also made soldiers live upto the stereo type of being heartless thugs who rape women and beat people.
It was also kinda silly how like 1 or 2 infected took out a team of trained soldiers with rifles in a house, that should not have been possible.
Overall though it is the best film in the zombie genre by far for me.