CBS hands down.
Both for picture quality, and surround sound quality.
The CSI's all look spectacular and The Unit has the best use of 5.1 surround I've heard on a Network.
(yes, I work for a CBS affiliate, but that doesn't mean I watch more CBS programming)
All said and done, the affiliates in these parts do a pretty good job.
(there is a current issue with ABC's audio lag, but I hope they are working on it before premiere time)
I do most of my Big 4 Network watching via OTA, so DirecTV doesn't really factor in.
CW I can only get via OTA, as well as PBS if I was inclined to watch it.
phox