Though referred to as a musical, Webber's "Phantom" is an opera in form. It is through-composed with very little spoken dialog. It is however, still a hybrid, since written for music-theater voices rather than true operatic tones. This has always been the one big flaw with the show as a whole, since it is hard for an opera fan to believe in Christine as an operatic soprano. Instead, the role is always performed by someone with a light, sweet voice, which, however beautiful, would not reach unamplified to the upper galleries of a grand opera house.
Emmy Rossum looks beautiful and vulnerable as Christine Daae, and has the voice that has become standard for the role--which, as I say, isn't really belivable for a diva-in-training, but that's Webber's issue. She does have a lovely voice. Patrick Wilson as Raoul de Chagny is stalwart and handsome and sings adequately, but not memorably. Gerard Butler as the Phantom seems a curious choice: his face is too pretty, but his voice is not. He overdoes it on the role's harsh portions. Perhaps his good looks are intended to heighten the shock of the revelation of his "real" face.
Supporting casting was somewhat curious. Minnie Driver obviously had grat fun chewing the scenery as La Carlotta, but why bother to cast her when her singing has to be dubbed, and her "star power" such as it is really isn't going to add to the movie's saleability? Surely there are plenty of singing actresses that could have done as well?
Some critics felt that the orchestral score sometimes drowned out the singing, which I felt occurred only on a few phrases. This may depend upon the theatre you hear it in. I generally felt that the soundtract was more distinct than hearing it live, and the film has the added advantage of close-ups.
All in all, good fun if you like music theatre at all.