What was said above about aspect ratio is the key. Assuming an anamorphic transfer, movies that were shot in a 1:85:1 aspect ratio like Batman, Jurassic Park, Silence of the Lambs and, IIRC, BTTF should present no black bars. Maybe a smidgeon, as 16:9 = 1:78:1. But still, very little on the whole.

Meanwhile movies shot in 2.35:1 like Star Wars & LOTR will still have black bars. Just not as much as on a 4:3 TV.

Ben-Hur is even wider, so it will have thicker black bars in order to present the whole image.

On the other hand, Full Frame classics like Snow White and The Wizard of Oz were shot in 4:3 so they will actually give you black bars on the left and right while filling the vertical dimension to the top.