I think Casablanca was a classic due to its on-going suspense and mystery. It was able to keep the views captivated til the very end. Not only does it include two men vying for the same womens love in a love triangle, it also deals with wartime conflict which many people from that time period could relate to.
All the characters added humor and drama through the clever dialouge but the one who stood out to me the most was Rick. His whit was unbelievable, and he gave an impression to be ignorant and selfish but in the end we see that he only wanted the best for Lisa.