Casablanca is considered a classic because it is timeless. After more than 60 years (released in 1942) the characters and the story still ring true. I can see Tom Hanks and Stephen Spielberg making this movie today. Add to that the stunning beauty of Ingrid Bergman (does anybody cry that pretty?) and the cynical bad boy character of Rick played by the incomparable Humphrey Bogart, and I can understand the accolades and respect this movie has been given. The screen sizzles with Rick and Ilsa's unspoken feelings for each other.
What stood out to me this time is the dialogue. Rick's cutting and witty repartee with the other characters, especially with Capt Louis Renault, are wonderful. The dialogue (so much of it considered Hollywood classic movie quotes) is another character in this movie.
The Club is the perfect backdrop, including Sam, Sacha (the waiter), Carl, and the drunken girl who pined for Rick. It supported Rick's character and rang true to the man he was.
I would suggest renting and watching this movie another time. You might be surprised at how much more you catch.