There are a few important missings. Just to point one, the Googles's original UI was as revolutionary as many of the examples here.
We give for granted now that applications should be clean, focus, etc, but for many years that was not the trend. To put it into perspective, its major rivals at the time (Yahoo, and MSN) followed the opposite path.
Google had a huge impact on how web interfaces are done today.
They also popularize ajax when they launched gmail but that its another story.
If anything, Google was a return back to spartan interfaces after the initial batch of search engines got too caught up in portal mania.