This frame from the 1.66:1 version of On the Waterfront shows off the definitive one out of the three aspect ratios included in Criterion's outstanding new Blu-ray release.

Don't trust any "reviews" that lack evidence that the reviewer watched all three versions. Likewise, trust no one who declares 1.85:1, aka "fill my whole HDTV screen ratio" the definitive way to watch. All who do are charlatans, fools, and rank poseurs.