Unfortunately, most people don't do the genre any favours. There are way too many people who get interested in Star Wars and from that time on, consider themselves serious fans of science fiction. Never bothering to see the classic films of science fiction or read the breakthrough novels of the golden years of the genre.
Anyhow, here are the three main reasons I believe science fiction is so good:
1. Possibilities and Ideas
Most people seem content reading kitchen-sink drama novels and wasting their life on shows like Neighbours. Wouldn't you rather spend your leisure time exploring the possibilities open to mankind? Ponder the future directions we may take and theorise the scenarios? I love science fiction because of the ideas it presents to the viewer/reader. What other genre give such freedom to explore the nature of consciousness, the morality of genetic manipulation, the ethics of societal intervention and the effects of war on the human psyche?
2. The truly foreign nature of the genre
Where else can a person experience a truly alien culture except between the pages of a science fiction novel? A hundred years ago, a western visitor to Japan would have been overwhelmed by the strange, alien nature of the country. However, advances in communication have transformed the alien into the commonplace. The only place I can experience a reliable sense of otherness is in a great sci-fi read or flick, like David Brin's Uplift Universe or Doc E.E. Smith's Lensman series.
Reality is just so limiting. At the end of a hard day, I would like to get away from the doldrums of day-to-day life. What better way then by immersing yourself in another universe?