Sometimes the subtle refinement is the invention. Pinch-to-zoom is a perfect example. If you look at many of the predecessors, the gesture was a command, not a manipulation. The pinch was disconnected from the actual dimensions of the thing being pinched. Look at Minority Report and you'll see lots of examples of gesture commands of that sort.

The remarkable thing about the iPhone pinch-to-zoom was that it was direct manipulation. You stick your thumb on London and your index finger on Dublin, then move your fingers to exactly where you want those cities on the screen, and the map zooms and rotates to keep the cities under your fingers.