History Channel: Featuring an endless diet of 2012, Nostradamus, and other superstitious nonsense, it's only a matter of time before they rename it the Hysteria Channel. People used to mock them as The Hitler Channel for their constant diet of WWII footage. It turns out that, thanks to the new management, that was actually the editorial high-water mark for the channel.
SyFy: It used to be called SciFi. And it used to have things worth watching, as opposed to a stable of in-house actors rotating through the same formulaic "monster/alien/robot threatens earth" cheapie.
HGTV: Some of the home/yard improvement shows are still worthwhile. Not so much: room makeovers slapped together under arbitrary time constraints ("we'll transform this kitchen in just 2 days!") imposed purely to inject some fake tension into the proceedings. When I watch a "carpenter" build an entertainment center in an hour by end-nailing a few boards of MDF and rolling on a coat of paint, I have a pretty good sense of how crappy that thing will look about six weeks after the cameras have left. It's going to make your student dorm IKEA bookshelf look like an heirloom. The only good thing to say about HGTV these days is that at least the housing market crash put an end to those stupid get-rich-quick property flipping shows. It's also pretty amusing to watch those "we'll stage this house and get it sold!" shows where at the end the voiceover admits "It's been six weeks since the open house and we've had lots of traffic. Our sellers are just waiting for that perfect offer" (read: all that work, still no buyer.)
Food Network: Anthony Bourdain already said most of what needed to be said about Food Network's decline into the celebration of mediocrity so I just need to add: what is the deal with all the competitions? Whether people are racing against the clock or competing against each other, like HGTV the artificial deadlines are imposed purely to create the illusion of drama. Food doesn't need that. Food is not theater.
Maybe we're coming to the end of an era, and single-subject channels are dying as a species. Meanwhile, the broadcast networks have become a wasteland of so-called "reality" programming interleaved with CSI knock-offs and Law & Order spin-offs. The only broadcast show I regret missing is the brilliant (in every sense) and under-appreciated "Better Off Ted".
So what does that leave? Well, for me it's basically USA Network: White Collar, Burn Notice, and re-runs of NCIS. Not exactly brain food, but still better than what's on elsewhere.