I think OP means compared to other kinds of fantasy and science fiction. In my opinion, this is related to technological development in movie-making, and also www in the 90s. So it is the other way around with space travel sci-fi, in my opinion.
Presentation of space travel, space ships, life in space and in space ships; set in space movies roughly have the same visual elements. And that has been done long ago up to a satisfying scale. Because of the nature of the concept, there is no room for a dramatic change in its elements. There is little room in space for anything as the basics go. It's space. Of course, it gets better, more realistic but there isn't anything completely new you can show.
But then in on the earth themes, the action, the style of the simple action presented in movies jumped a scale. Esp. when the camera, shooting technology changed in the 90s if I am not mistaken. (The Matrix for example.)
Well, with themes on earth you always have more room to tell as it is our natural habitat, but now you also have 'more' to show with the new technology, now you can make a simple fight scene an 'epic' event. This new technology makes a dramatic difference in visual presentation on earth themes, but not so much in space. Also, before this technology, it was difficult to make women and children play hardcore traditional action scenes.
Then came The Lord of the Rings and changed the movie-making altogether, because we hadn't seen anything like that before. Then everything had to be 'epic' in a certain way.
I think this is also one of the reasons why the Vampire genre exploded at the beginning of the century. There is nothing new in that compared to the traditional elements either. The actions, movement, the scale of the show got bigger. It's fun watching them for a while, but they are action movies in the end. But then, I think Jim Jarmusch showed that the vampire genre doesn't have to have action with Only Lovers Left Alive and also Thomas Alfredson with the 'Let the Right One In'. Great movies.
The 90s are also the years the world wide web went into peoples' hands. First public web pages, forums, message boards. So this time people also had a new medium to take all this, make their own and create new subcultures. Just by itself, The Matrix boosted internet usage. By the 2000s it became a force by itself. It took time for the old, classic sci-fiction to become mainstream again because it needed a new kind of popular culture to make references to old movies and series in new ones. Now recognising those references in movies and series alone is a sign of high culture in mainstream culture.
To me, a good sci-fi (based on a sci-fi plot rather than sci-fi ornaments) in space is pretty much the definition of 'epic' by itself. It's in space, lol. We should have been up there traveling by now.
