The Lumière brothers initiated commercial cinema with "La Sortie de l'Usine Lumière à Lyon" (alternately called "Workers Leaving the Lumière Factory", "Employees Leaving the Lumière Factory" and "Exiting the Factory" in English). The brothers made what they call actuality cinema: minute-long documentaries about mundane topics. In this case we see a bunch of people leaving a factory. The plot won't look like anything spectacular to people in the 21st century, but you have to realize what things were like when it debuted. To see a moving image was something new. Martin Scorsese's "Hugo" focused on cinema's infancy (and showed how the clip depicting a train's arrival scared people because they thought that the train was going to hit them). Sure enough, cinema became the 20th century's dominant entertainment.
Not any sort of masterpiece, but worth seeing for the historical context.
Not any sort of masterpiece, but worth seeing for the historical context.