I disagree. Google's search engine was orders of magnitude ahead of everyone else's when it came out. Like it actually worked vs all the others that did some mediocre keyword matching and could be moderately useful if you were good with boolean operators.
Gmail, which another poster described, was also mind blowing at the time.
Google Maps, and the fact that you could scroll across a map smoothly was mind blowing at the time, and really redefined what was possible with xml http request, and "web 2.0"
These are the biggest that come to mind and its somewhat telling that Google Maps was the latest, and I believe launched in 2005 or 2006.
There were lots of other products that were less impressive, but definitely a step ahed of just about everyone out there- google finance, the "office" suite- do kids in school even install MS Office anymore? It used to be a defacto must have piece of software, I haven't had it on a personal machine in years now...
And a lot of stuff that looked like it was going to be something very big, but died on the vine. Google Voice, Google Reader, Google Image search come to mind here.
Then from a pure tech side of things, Go, Kubernetes, Node.js, the early hadoop and "big data" tools, all came from Google as well. But maybe getting back to your point, their backend stuff has not really turned into an "astonishing" user facing product in quite some time.