Ping isnt a very good determination of latency on a network. Assuming that you are a Comcast subscriber, its not surprising that you see less latency to Comcasts DNS servers than to Google since you are on the same network as Comcast and not going over the public net.Google public nuisance?
Better with this free service. OpenDNS | Internet Navigation And Security
I ran a ping test on Google DNS yesterday and found the same latency. (Edit- It's even worse today! LOL) Comcast beats them both, however I like the security of opendns, and I'm sticking with it as do many schools, businesses and other security conscious, savvy users are.
Now if Comcast would have something like this attached to your account with a web-based user interface for parental control... $$$$ Most people have never heard of opendns and wouldn't know the first thing about how to use it.