Is this the oldest movie that general audiences of today still watch? I mean is there an older movie that could air on TV or be rereleased theatrically and still get a sizable audience of mainstream (non-“film buff”) viewers?
Interesting question... certain silent films certainly still have some degree of mainstream following - Chaplin, Keaton, Laurel & Hardy, Harold Lloyd used to be shown in morning/afternoon weekend slots on TV when I was a kid in the 80s, I remember.
All Quiet on the Western Front maybe qualifies, too - it’s still an immensely powerful and accessible film for modern audiences.
Metropolis is actually a good one... I remember I first saw it when the DVD was given away free with a national newspaper, back in the 90s some time... I think it has probably been quite widely seen when compared to the majority of silent classics - I hope so, anyway!
I think it's the popularity of the horror genre that keeps this movie where it is. If original posters for horror movies is anything to go by, then this one beats them all. An original poster (the blue one that Moviechat currently show) has sold for $525,000. The only earlier movie in the list of original horror poster values is Lon Chaney's 'The Hypnotist' (1927).