Unless you count their joint appearance in The Longest Day, El Dorado deserves its place in Hollywood history for being the only co-starring effort of John Wayne and Robert Mitchum.
Besides being good friends Wayne and Mitchum were both known for being able to drink just about anyone else in the film business under the table and still report to work in the morning, lines letter perfect. But Mitchum was not allowed in the Wayne home because Pilar Wayne never forgave him for ruining their honeymoon when Mitchum backed out of Blood Alley and Wayne had to star as well as produce it.
I also think that the Duke was leery about Mitchum stealing too many scenes which he does when they are on the screen together. In this tighter and faster remake of Rio Bravo, Wayne is his usual stand up hero, rough and tough, but who lives by a code. Mitchum is the flawed one. During an interlude of several months in the film, Mitchum becomes enamored of an unseen woman, loses her, and becomes a drunk.
Which leads me to one of the funniest scenes ever in a Wayne film. When Christopher George and fellow gunmen are hired by villain Ed Asner to run R.G. Armstrong and his family off their ranch, Wayne has to sober up Sheriff Mitchum and fast.
Every time I watch El Dorado, I get hysterical every time I watch James Caan pour a homemade remedy down Mitchum's throat with Wayne and Arthur Hunnicutt holding him down. And the reactions afterwards, absolutely priceless. This is where Mitchum steals the movie.
As in many a Howard Hawks film, there is a theme of professionalism that runs through it. Whether it's Cary Grant and his fellow pilots flying over treacherous terrain in South America, Humphrey Bogart with his charter boat business in the Caribbean, or Wayne and Mitchum going up against fellow professional Christopher George, it's doing the job and doing it well for it's own reward.
The final gunfight is also a classic. Let's just say that Mitchum and Wayne are not at their best, but they make up for it with some help from interested friends.
This is one of the best films, in the top 10 for both these guys and shouldn't be missed.