(If you haven't seen On the Waterfront, please don't watch the clip. See the whole film first. This scene won't have the same impact out of context and seeing this clip will ruin the experience of watching the film. If you have seen the film, click and refresh your memory.)
I've had a request to go deeper into the Brando thing, so I will. The first thing I want to say is that it takes more than acting chops to produce a result a great as Brando produces. The role has to be crafted a certain way.
There are three types of conflict: character vs. character, character vs. circumstances and character vs. self. The first is the most obvious and it's where most animated films live. It's just good guys and bad guys. These characters may be very entertaining, but unless there's also the other kinds of conflict, they remain shallow. Cruella de Vil is beautifully designed and animated, but she's a flamboyant piece of cardboard. There is nothing complex about the character. She has attitude and nothing else. The same is true for characters like Shere Khan and Capt. Hook. All these characters have one track minds and the writing and acting challenge is to find a way to make them interesting to watch. It's not easy and I'm not minimizing the creativity and effort that goes into these characters, but ultimately they are simplistic.
The above Brando scene, on the surface, is also character vs. character. Rod Steiger wants Brando do something and Brando isn't sure what he wants to do. Steiger decides to let Brando go rather than force the issue. But the scene is far richer because it is also character vs. situation and most importantly, character vs. self. Steiger can't acknowledge that he sacrificed Brando's career for profit. Steiger pulls a gun on Brando even though he loves him. Ultimately, he can't go through with using force and lets Brando get away. Steiger is balanced between loving Brando and manipulating him and the scene revolves around what Steiger will do.
Brando is torn between what Steiger wants him to do and what he dimly perceives is right. He knows that Steiger has betrayed him in the past and caused him great pain, but he still loves Steiger. His position leaves him with no self-respect and he senses that he's got to change if he's going to survive, but he knows that changing is going to be painful and dangerous.
It's not simply who's stronger or more clever. Each character has to make decisions that define who he is and each knows it. Each decision has a huge moral implication. Is there a scene anywhere in animation that is as complex as this one? That's not a rhetorical question. If there is, I'd love to know about it.
Many actors would have played this scene less effectively than Brando and Steiger, but at least they would have had something to work with. Brando was in many films where the writing couldn't support his abilities and the results are not effective. There has to be a well-developed role before an actor can do his or her best work. Being Brando or as good as Brando isn't sufficient.
In animation, there are two things working against the possibility of a scene like this. The first is that the writing isn't ambitious enough. I'm not saying that every animated film has to aspire to the power of this scene, but not enough of them do. Children's entertainment has been dumbed down and made morally simplistic. Family films are more complex, but because children are part of the audience, the film makers are afraid to upset children or present characters who are beyond a child's understanding. The cost of animated features is a powerful incentive to not offend or confuse potential customers.
(In animation's defense, large budget live action films have fallen into the same trap. The live films that have avoided this are lower budget and released in time for Oscar consideration. They're delicacies that are only in season for a few months a year.)
The second problem is that even when animators are cast by character, they're still sharing the character and so developing a complex personality is next to impossible. That's one reason why voice actors are so important in holding a performance together. Brando was unique, as are all good actors. It's impossible for several animators to be unique in the same way. Instead, their uniqueness has to be sanded down into something closer to average so that their scenes can fit together.
Are there animators who are capable of a performance like Brando's? Perhaps. But the story material isn't there and the industry isn't structured to give animators the chance. In essence, we've limited the writing possibilities and put animators on a short leash, so it's no wonder that the gap between animated and live acting is so wide. And to be clear, I'm not arguing for animation that imitates Brando's acting. What I'm looking for is animated acting that creates the same powerful effect on audiences as Brando's.
I mentioned Gollum because the character was conceived with the same level of complexity as those played by Brando and Steiger. Gollum is also torn between choices that have moral implications. Anyone familiar with Tolkien's books knows how the film will end, but Gollum's success on film comes from how convincingly the character wrestles with his choices.
For Peter Jackson and Andy Serkis, this type of character is part and parcel of what they do. Serkis has played Shakespeare, who fills his plays with characters of this type. Hamlet, MacBeth and Othello all have to make morally difficult choices that determine their fates. For animation, this kind of character is rare or non-existent. A character's choices are usually unambiguously good or evil.
There is room for all kinds of animation and all kinds of animated content. I'm not arguing for a single standard. But what future does a medium have when it voluntarily abandons the aspiration to create work that compares with the best of other art forms? That's what animation has done and it's why there's no animated equivalent of Brando.