Science Fiction is a setting (not a genre) that frequently gets written off and ignored because it’s deemed inept to deal with more serious topics. But science fiction has leave to deal with heavy subjects in a way ‘regular’ fiction only wishes it could. Science fiction – good science fiction – has and will always be about people.
The world will change, but people will always stay the same. People will always want to control, people will always want more, people will always want love, people will always yearn for adventure, and people will always want to find home. It doesn’t matter if it’s the 17th, 21st, or 26th century: people don’t change. The best science fiction examines humanity – consciously or not – in ways that other fiction can not.
Ender’s Game can easily be looked at as just another story about mankind repelling alien invaders. We’ve got the buggers/formics poised to destroy humanity and the only hope lies in the kid named Ender Wiggen. But it goes beyond that: it looks at the idea of empathy (and the lack of it) as a tool and a weapon. It is Ender’s immense capacity for empathy that makes him an excellent leader and brilliant tactician, but it’s his ability to withhold it that makes him a brutal opponent. His empathy endears Bean, Alai, Petra and others to him, his brutality puts a very permanent end to his victimization. It’s this ability of his that allows him to understand his utterly alien enemy and defeat them, but ultimately come to love them. Because he understood them he could love them with all his innocence.
Ordinary fiction would spend too much time trying to explain how and justifying why child soldiers were being trained the way the International Fleet trains Ender and friends. The concept of an enemy so completely unknown, so plain inhuman would feel terribly contrived in conventional fiction. In Ender’s Game we go with it because it’s the setting. We get the innocence of a child and truly alien enemy. Why? Science fiction.
Everyone dreams. Everyone wants to escape. Inception gives us a world where we can escape into our dreams. Yes, there are practical uses for this (typically of the espionage and thieving variety), but what would we really do with this technology? Would we would run from the world and its problems into our dreams, into dreams where everything is how and as we want? Christopher Nolan examines the concept of being able to escape in this fashion and the questions of reality that ensue. If our dreams are better than life would we not chose to stay in that world? What would reality mean then? What would we do?
In Inception we see people running from reality and trying to create their own. It’s what we do in our daydreams and it’s what we do when we go to the movies. But in the world of this movie it’s something they can do on a whim. Some people hide in them, some people will use them, and some simply remain unaware. It’s on the humanity within the story that science fiction thrives. We see people act and can’t help but to wonder whether we, like Cobb’s wife, would just want to live in our imaginary world.
Finally; Serenity. The idea presented in Joss Whedon’s film is the question of control. Of course, we’ve heard stories about totalitarian governments clamping down on freedom and forcing them to behave. But it’s in this setting that the Alliance has not only the will but the ability to truly control their population. If free will and the capacity to make choice is taken out of the human equation what then remains?
Science fiction allows us to explore the idea in a world where it’s possible. Because we’ve agreed to believe that the technology exists we can see the implications. Serenity asks what would people would do if they found a world without choice. Five hundred years in the future we will still aim to misbehave: especially if misbehaving is the right thing to do. Set against a backdrop of spaceships and planets is the story of an artificial family just trying to live their lives and find some semblance of home.
So why science fiction? The setting lets us create worlds where the impossible is just a part of life. This impossible factor lets us ask what people would then do. District 9 asked the question of aliens and segregation, Alien created a unique horror film, Jurassic Park demonstrated the fallacies of playing god. Sure, the setting can be seen as just a vehicle for a parable, but it’s a world where imagination runs wild.
Good science fiction is about the people in the world. It’s a simple concept: the world will change but people will stay the same.
Plus, science fiction is just so friggin’ fun.
Essays, Not Rants! 
A lot of science fiction is used as metaphor or allegory to present or try to explain who we are now – District 9, Battlestar etc. But I would disagree that the thesis of all science fiction is that technology or environments change, but people stay the same. Certain genres of science fiction assume that we are capable of change – that we may be biologically, socially or even psychologically different – or that change is evolutionary. Some science fiction is interested in the future as a distinct “potential”. Now we look back at early science fiction to see it as a reflection of the preoccupations of its times, but that is/was not necessarily its intent.