Epic films are nothing new. In many ways, most science fiction films try to be epic. Most of them fail and I have stumped upon the single element that leads to that failure or success.
Fans of Star Wars almost universally agree that The Empire Strikes Back is the best of the saga. There is a reason for that. I used to consider the first film (titled simple Star Wars or A New Hope depending on your level of purism) the best and in many ways it is, but it was really eclipsed by its sequel in virtually every way save the ending. Empire is the middle chapter, yet it holds its own. The secret lies in the choice of director. Irvin Kershner was known for his personal, intimate style. He didn't tell epics, he told stories of people and that is what Empire is.
If you take a look at the Star Trek films, you find much the same thing. Why were the second and fourth movies the best? They told very personal stories. The second even manged to do so without having the two main opponents on the same set. A brilliant piece of story telling. The fourth film does it by making it about this small crew going home to face the music for what they have done and finding a way to save the planet in the process. These films are about the people. Plus they tell a pretty great story.
When the creators of a film realize this little secret, they hit gold. William Wyler did this for MGM in 1959 with Ben-Hur. He was the director of very intimate, personal movies. Yet here he was making the largest and biggest budget epic to date. That was the success of the film. That is why so many films fail. They fail to realize that a good story is first and foremost about the people that inhabit it. When the creators of a film realize this, the film succeed because all their choices are focused into telling the best story they can and if the background is epic, the picture is epic.
This holds true for the written word as well. All stories are about the characters and their journey. A well crafted tell can tell anything on top of that and can do so with many characters at the same time. Movies usually need to pare that down a bit and focus on just a few, but a few rare movies can capture that even with a large cast. But no matter the scale, the film needs to be intimate. You need to get close to the characters. You need to feel their journey. When you watch Han and Leia fall in love, you believe it. When Leia reveals her feelings, there is no doubt because the stage has been set. Han responding with "I know" just tops it all off.
Love, is of course, not the only intimate tale to tell, but it is a very common on. Stories fail when they fail to make the story intimate and personal. In Battlestar Galactica (1978), you care about the people. You quickly get invested in their journeys. In Galactica 1980, the characters have great adventures, but you don't get to know them at all. There are no moments when the characters reveal themselves.
Generations have followed Frodo to Mordor because Tolkien invested his tale with intimate moments where the characters come alive. Yes, the story is of great adventure and he was a great world builder, but the success comes down to the reader caring about Frodo and the story being so much about him and his companions more than the War of the Ring.
Same for the original Star Wars trilogy. We care about Luke, Han, Leia, and the others, because the movies are intimate. Here they are toppling the great Galactic Empire of Palpatine, and they story is not just about the battles they fight, it is about their friendship, their relationships, the other events in their lives, as much as the battles.
So great story telling, no matter the medium, is that intimate connection to the characters that bring them, not just to life, but close. Like you know them personally.