So what's the most difficult part of reviewing silent movies, you might ask. That's easy: the fact that something like 80% of them no longer exist.
For a case in point, take Cleopatra, the 1917 blockbuster starring Theda Bara. It was far and away the most popular movie of that year. Not only did it finish atop the list of top grossing movies of 1917, but you see references to it all over the place—for example, Roscoe Arbuckle spoofing Bara's famous dance in his comedy short The Cook (which you can see here).
Unfortunately,the last print of Cleopatra was destroyed in a fire in the 1930s, not an uncommon fate for films of that era which were printed on silver nitrate—nitrate being a key component of gunpowder.
All that remains of Cleopatra are some stills and a legend. Unfortunately, it's impossible to judge a silent film by its legendary status. Too many times, a lost film has acquired a reputation for greatness, then been rediscovered and turned out to be a tremendous letdown. Based on stills alone, Alla Nazimova's Salome, for example, was considered a classic; then the film itself was rediscovered and turned out to be a train wreck, nearly unwatchable.
Add in that Bara's fame was very brief—only about four years—and that her most famous surviving film, A Fool There Was (1915), reveals a rather stiff performance, and I'm inclined to think Bara's success was more a matter of notoriety than actual talent. I could be wrong—lots of people will disagree—and if a complete copy of Cleopatra turns up in somebody's attic one day, I'll cheerfully revisit the question.
Anyway, here's all that remains of the most popular movie of 1917, Cleopatra:
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