Gravity director Alfonso Cuarón told Wired that, while he loved every second of it, he will never do a space movie again. The four-year process was so complicated that it's a miracle that it worked at all. Reading about how they did it is truly incredible.
Consider this: They first had to make the entire movie as an animation with actual sound, music, and lighting. The most intricate storyboard ever created. They kept adjusting it forever and, only when they were completely happy with it, they moved into actual filming.
After that, Sandra Bullock and George Clooney had to train to execute extremely convoluted dancing-in-space choreographies with perfect timing. They became Russian ballerinas doing their numbers suspended in a virtual reality box.
Only when everything was perfect they started the actual filming process. And then they had to put it all together in one seamless and glorious whole. IN 3D! Let's not forget about the 3D component, which only added to the difficulty of the planning and filming. Gravity is perhaps the only good use of 3D after Werner Herzog's Cave of Forgotten Dreams.
Technically, Gravity is already one of the wonders of moviemaking history. I can only think of Alfred Hitchcock's Rope—which completely changed conventions by making the entire movie in a single sequence, only interrupted to change the film rolls—as a similar feat in terms of planning and perfect execution. I'm sure Hitch would have used animation to plan his films too. He always made meticulous storyboards that resulted in movies that required almost no editing at all.
And on top of that, not only Gravity is technically perfect: It seems that everyone loves Gravity because of the story and acting. A must watch this weekend.