Something for everyone
Casablanca is considered one of the greatest films of all time for a reason. While old, it is not dated, and I doubt it will ever become so. This is helped by the fact that it is meant to be rooted in a very specific time and place, rather than a generic "now" at the time of filming. And, unless your taste runs exclusively to explosions and special effects, it appeals to a variety of tastes. It has action, intrigue, romance and comedy. The characters are vivid and three-dimensional, and the acting is excellent. How can anyone not like it?