The Motion Picture Production Code was in force from the early 1930s to the late 1960s. Its guidelines around sex (copied below) limited the types of kisses seen on screen, making them much more chaste than what has been allowed in subsequent decades. Here are the top kisses from that more restrictive time.
2. Scenes of passion
(a) These should not be introduced except where they are definitely essential to the plot.
(b) Excessive and lustful kissing, lustful embraces, suggestive postures and gestures are not to be shown.
(c) In general, passion should be treated in such manner as not to stimulate the lower and baser emotions.