watch this movie if you know what you get. When you see such a movie you can't expect a great story, deep connection with the characters nor a good video game adaptation. However you can have fun especially if you watch it in 3d the scenes are quite amazing, fights are good,the music is thrilling and Milla is hot! I don't understand how people can't get this and have different expectations about the movie. It's like a theme park ride, a fun one and if you get it, you get it if not.. whatever. I enjoyed this movie more than the first 3, probably because I watched it in 3D, the scene where Alice jumps off the roof combined with the music got stuck in my mind and is just breathtaking.
TL;DR: watch it if you can enjoy a movie just for the sake of the action scenes,zombies, effects.If you're looking for something original/deep maybe you should watch something else.