Ever since this came out in the theatres, I've always been puzzled about the reasons why it didn't do better. Perhaps, as some other reviewers pointed out, it is because no one recognizes who The Shadow is anymore (however, although I'm far too young to have heard any of the radio broadcasts, I was at least familiar with the existence of them and had an idea of their general style, as anyone with a basic knowledge of American pop culture would). Perhaps, on a related note, it is because the writers stayed relatively faithful to feel of the old radio shows and resisted the temptation to "update" it which, although one of the best things about the movie, doesn't generally make for high box office sales. I've come to the conclusion that "The Shadow" was simply ahead of its time. If it had been released in the last couple of years, as people have learned to see and appreciate camp for what it is, it would have done much better.
That having been said, this movie is absolutely fantastic. The casting was dead-on (I've never seen Alec Baldwin in a yummier or more suitable role), the sets and costumes were stunning, and the plot and dialogue did an admirable job of walking the fine line between campy and cheesy, achieved by restraint in all of the right places. All of that, plus a killer ending that was completely unexpected but couldn't have had more poetic justice about it.
I highly recommend this movie - you'll want to watch it again and again.