It had a clean user interface, especially compared to the others at the time. Early on it published a series of shortcut commands some of us still use. If you type define:[someword] it will return a definition. You can also pass common scripts and even mathematics to it and it will return what you expect. That is a really handy tool and nerds loved it.

What really sealed the deal, though, was its purchases of YouTube and DoubleClick. With ad information and being the defacto search engine for internet videos gave Google the behemoth status it has today.

I forgot about Keyhole, that was a big deal too. With that acquisition they became the default search engine for geographic data.