City Lights (1931)
Suggested by Breumaster
Worldwide: Doc Brown lends you his DeLorean with a proper flux capacitor and two loads of plutonium to travel 100 years back in time to the year 1918, when movies were young, and then back.
What movie - as selected by the IMDb poll board users - rated 7/10 or higher with at least 10.000 votes - would you most likely show your fellow countrymen in past time to see their reactions and tell us later?