The thing that those 3 have something in common with their search engine and Adwords; they all inspired the same initial reaction: "Someone's finally fixed what's wrong with incumbant market players - this is a game changer". Do you remember what it was like in the days when spammed to death AltaVista, "2MB inbox" Hotmail, static image Multimap, clunky WinMobile and popups/animated gif banners were the kings? (Android is not quite the same, since the iPhone had pointed the way).

I've not seen that many software products which were so obviously disruptive; it's no wonder they became giant-killers. Facebook is the only other one I can think of.

On the other hand, some of their other big products have not be a huge success precisely they haven't been game-changers. Google Docs, for example, might be a good example of a web office suite; but it's hardly a game changer as far as office suites go, because it doesn't do some of the core things that people do daily with office suites. It was clear from the beginning that it would be a slow starter. Whereas Maps for example, you knew at the beiginning that nothing else could touch it