1968 was a year of great adaptations, from musicals, novels, and history, with the occasional original screenplay.
Along with the fact that these films are now 50 years old, it's interesting to compare these adaptations to their original source material, and then again to remakes that may have come out since. For example, in the case of The Lion in Winter, about King Henry II of England, it's interesting to look at non-fiction or historical fiction that has come out in the past 50 years to see what we have learned since or what is interpreted differently now.
50 years is a long time, and cultural attitudes had plenty of time to change in the intervening years. That said, here is a list of films that turn 50 as of this year.