I love Argento to bloody pieces, but this was too self-indulgent for even me, and it seems mostly like a vanity project. About as interesting as a corporate training video, the best thing that can be said about "Il Fantasma dell'opera" is that the sets are typically opulent, although you may rightfully wonder why the Phantom's "underground" lair is so surprisingly well-lit. What is the light source? There's good stuff involving some demented rat-catching, too, and Argento injects some variation into the Phantom myth: instead of being disfigured, he is normal-looking, and has simply been raised by rats. Well, something like that.
This definitely wasn't a breakout role for Asia Argento either, although she eventually did become recognized in her own right. As far as Argentos go, this one is best viewed maybe only once, just out of curiosity. Dario did this same theme much better in his own variation simply titled "Opera".