Sunrise: A Song of Two Humans (or just Sunrise is a 1927 film by legendary director F.W. Murnau. The film won the Academy Award for Best Picture back when there were two categories for it, notably under the category "Unique and Artistic Production". It would ultimately be the only film to ever win that award. The film is also noted to be one of the greatest ever made, having found many camera tricks and effects that we now only take for granted today.
In 1937, the film's original silver-nitrate negative predictably caught on fire, destroying the original negative. All that survives is a copy of the film in vastly poorer quality held by The Library of Congress. While the film is available on rare Blu-Ray and DVD copies from this print, a 35mm print is a long-sought-after rarity.
What makes this different than the grainy copies of many silent films is the fact that it's the camera work that made this film so innovative. With many shots being very hard to make-out and many of the double-impositions that were used being blurry, it is hard for many non-film-savvy viewers to get what all the hype is about. To add some perspective, other silent innovators such as Fritz Lang's Metropolis and Carl Theodor Dryer's The Passion of Joan of Arc have gotten high quality remasterings that offer crystal-clear depth to their images. Even the Blu-Ray version contains many blemishes and blurry elements. This means that even in high definition, Sunrise is still in vastly inferior quality. While many silent films have fallen victim to this, none of them have had the impact on the history of cinema as this legendary film.
Update: With the film having been re-re-released on Blu-Ray, this film has been successfully cleaned up by modern day technology. While a high quality print remains undiscovered, thanks to advances in restoration software, Sunrise can now be viewed in much better picture quality.