I suppose it's debatable. I'm talking about stuff like the iPhone singlehandedly revolutionizing the touchscreen mobile market, and the iPad essentially creating the tablet market from scratch - they existed before, but were pretty much uniformly awful and I can't remember anybody ever wanting one.
It's not like email or webmail didn't exist before GMail, but I suppose you could argue that the revolutionary at the time use of AJAX plus gigabyte standard storage space, plus great spam filters was enough to transform webmail from a handicapped second-class citizen to something that tech experts would be happy to leave desktop email clients for.
But then, Google Maps was better than the competition, but enough better to be a revolutionary difference? I'd say no. But where do you draw the line between a good refinement of a pre-existing class of application to something that qualifies as revolutionary?
