Great Thread. Seeing as how I'm somewhat in the industry...
The Great Escape! An Excellent movie that got shafted at the oscars because of...
All the President's Men (another great film)
The Big Lebowski (Careful, man, there's a beverage here!)
Ghost Dog: Way of the Samurai (With Forrest Whittaker. If you have netflix, rent it)
The Red Violin (Samuel L. Jackson in a very different / interesting role for him)
Like Water for Chocolate (Alfonso Arau is a great director)
Most Robert Rodruguez Films (El Mariachi / Desperado / From Dusk Till Dawn) if you like action.
The Odd Couple
Casablanca for sure, but how about...
The Third Man, with Orson Welles.
A Bridge Too Far
Dr. Strangelove (Mein Fuhrer, i can walk!!)
Most any Hitchcock film, my favorite is North by Northwest.
Operation Petticoat (Cary Grant / Tony Curtis on the pink submarine)
Hunt for Red October
American History X
American Beauty
And those are only the most recent on my Netflix 5-star list.
More ideas:
http://imdb.com/chart/top
Everyone has a bunch of movies they loved but can't remember...
BTW, Blues Brothers is my favorite movie. Trivia: John Landis' stepfather is the guy who blows the whistle outside the door at Joliet when Belushi first gets out. He was a great guy, flew top turret in B-17's during the war.