Nothing apart from search, ads, maps, Gmail, Chrome and Android was a huge success. They essentially created their own monocultural ecosystem.
Most of everything else was a short-lived fad. Plus, Wave, Reader, Chat and Glass, to mention a few.
Isn't that a selling point of Apple ecosystem as well? Everything just works
There's value in scale. The YouTube founders themselves said they couldn't have grown YouTube without help from Google infrastructure and other business functions. In the mid-00s people were just figuring out how to run an Internet business with billions of daily users; this is a service now externalized through Cloud providers (including Google), but back then "not falling over when you got Slashdotted" was a key competency that Google had but many of the thousands of other Internet startups did not.