I've seen this a few times, and every time find more to appreciate in it. A film that tells the story of Faust while itself being the story of Faust, while as well touching upon the themes of Dorian Gray and Phantom of the Paradise and Frankenstein as well. Brilliantly both Satirical and observant, ironic, touching - and - while appearing at first glance to be dated, not a little bit, not at all...
And - little observation - but is it possible - that the Phantom was the inspiration for Lucas's "Darth Vader"? I mean, compare the costumes...
This is a masterpiece that gets better every time I watch it.