I would have to agree that Gutenberg's printing press is the most important invention in the past two thousand years because it changed forever the cost of knowledge distribution. What other inventions wouldn't have happened if the inventor didn't have access to books? In a sense I think we can trace many aspects of our information society back to this single invention. In it's electronic form on the web we see movable type and a yearning for information to be accessible and free. The web is taking the cost of distributing information down near zero. Gutenberg would be pleased to see where his invention has taken us.
To arrive at the edge of the world's knowledge, seek out the most complex and sophisticated minds,
put them in a room together, and have them ask each other the questions they are asking themselves.