Yes, love the film, but I can say that about any Leone picture. It is nowhere as well known as his other Westerns. 

So, I will play off this with two films (plus one bonus film that is in the same ballpark as Duck, You Sucker) one that stars Steiger and the other that stars Coburn. 

First, if you have not seen it, check out Sergei Bondarchuk's Waterloo, with Steiger as Napoleon. The battle scenes that Bondarchuk shoots are epic and give you a fantastic view of how the battle was fought, won, and lost. Incredible and it is all done with real people, not CGI, we will never witness anything like it again!

When it came out, some critics bitched about Steiger as Napoleon, but personally, I think he kind of nails it. The other piece of trivia about this film was, because it flopped, the people backing Stanley Kubrick's Napoleon film backed out and he never got to make his picture. MosFilm restored it short time ago, and you can watch it for free on the YouTubes. It is gorgeous. 

Second film I will throw out there features James Coburn in the lead. It kind of is perfect for our time. It's called The President's Analyst. Yes, it kind of has a groovy 1960s vibe, because that was when it was made...but, satire baby, good stuff. I don't have a free link to this so, you will need to track it down streaming somewhere but here is a taste:

And the bonus film is A Bullet for the General another Italian "Zapata" Western in the vein of the Leone film. You can watch that for free here: