This used to be true, especially with Comcast, but I read a blog post about a year ago stating that in most cases using Comcast's DNS servers is actually faster nowadays.

I closely benchmarked it and they turned out to be right, though 8.8.8.8 had only a little bit more latency. And it makes sense; your ISP will always (theoretically) be able to provide lower latency than Google can when they put the effort into it. Unless Google is your ISP. :)