The examples provided are not relevant, because chartbeat also saw a hole in Google's offering, and filled it. That is exactly the same as all the sites you me

The examples provided are not relevant, because chartbeat also saw a hole in Google's offering, and filled it. That is exactly the same as all the sites you mentioned. The only difference is Google is now offering real time analytics. A counter example would be a service that provided a missing feature for a google product, that was later filled by google, but managed to survive after google launched the feature.