The Sci-fi / Western Hybrid Genre
Though Star Wars wasn't technically the first Sci-fi film set in space, it was the first that really blew audience's minds. Set entirely in another galaxy, including planet sized space-stations, solar systems with two suns and full blown space-ship dog-fights, it set the standard for space-epics in the future.
Another reason for its success was the take on the Western genre which had all but sizzled out by the 80s. The films included gangsters, shoot-outs and rebels against the government amongst other western conventions, reigniting the love of cinema that the generation of the 50s had with westerns and drawing in the new generation to the same genre in an updated, outer-space style.
Being such a huge hit in the 80s, Star Wars has got an even bigger cult following today. As well as the obligatory (and controversial) prequel trilogy and animated series, numerous video games have been released and a massive amount of literature detailing the years before and after the films were set, all of which can be sourced and read about online on the Star Wars Wikipedia page, Wookiepedia (named after a species invented for the franchise).
Of course, spin offs and parodies have also been made, referencing famous moments and themes in Star Wars, my favourites being Robot Chicken and the many It's A Trap videos poking fun at Admiral Akbar's slowness to realise an ambush during Return of the Jedi. There is so much to get engrossed in, the perfect place for a bit of escapism.
SPOILER ALERT BELOW!
If for some reason you haven't seen Star Wars, this is best saved til you do. If you have seen it already, I can safely tell you that one of the best parts of Star Wars (apart from the explosions, space dog-fights and pure awesomeness) is the fulfilment of the prophecy that one day a Chosen One would restore balance to the Force (balance seemingly meaning a return to the 'light side of the Force'). Throughout the whole trilogy, we are waiting for the hero of the films, Luke Skywalker, to do this but it is instead his father, the evil Darth Vader, who is the Chosen One.
As he stands by and watches his Master, Emporer Palpatine, kill his son with Sith lightning, he sacrifices himself to kill the evil leader and save his son. He finally turns away from the 'dark side', saving the galaxy from the Sith Lord's tyranny. However, in doing so, he kills himself, taking the effects of the lightning onto himself.
This sacrificial showing of love for his son is a beautiful moment and is the perfect ending to the saga. The reminder of God's love for us in this scene is one for another post, but that love is what humanity craves and is possibly the best theme throughout the franchise.