Except Gerrit's not really all that great either! It just looks good when everything else has been dumbed down to parity with GitHub.
This start up seems like they are trying to sort of package and iterate on the value and power of Gerrit: https://www.gitcolony.com
I literally came across this just now:
https://github.com/google/git-appraise
Although it may well be a decent Gerrit alternative - it still talks about interfacing with Jenkins.
There are projects out there with workflows where people submit to Github so the CI can run, then it gets pulled into Gerrit for code review on a website with no visibility into the result of that CI.
I'd love to move all code review to Gerrit but I'd need to see something disrupt this space first.