I've got a millennial cousin who thought a black & white movie can't be that good. Then he saw Casablanca and was blown away. A 30-something woman I know watches TCM all the time, and on her initiative we've seen many classic films in theaters, including Casablanca, The Wizard of Oz, Marx brothers, Philadelphia Story, etc.
i saw wizard of oz in a movie theater many, many years ago and it was the first time on the big screen. i had only seen it on standard definition, 640 x 480, television before that. probably hadn't seen it since very early '70s. i cried. that is an incredible movie considering it was made in 1939.
-- MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige. Bought June 2000 - Sold May 2010
My dad and my uncle saw its first run in a NYC theater. On the way home, my uncle amused other subway passengers with his Cowardly Lion impressions. Many years later, I saw him do it, and he was quite good. It helped that he looked a bit like Bert Lahr. (With some Rex Harrison thrown in.)