Good Eats is my favorite by far. Giant foam props and sock puppet theater in a cooking show? That's how you know it's not just a cooking show; it's a food show. Oddly, I'm not impressed with Alton Brown's Feasting on Asphalt, even when you consider my love of motorcycle riding (and unrequited love of BMW bikes).
For some unknown reason many of the female hosts really annoy me. Wait, I do know the reasons. Rachel Ray is overbearingly perky and her constant, cutesy abbreviations grind on the language section of my brain. Paula Deen's heavy-handed Southern charm gets obnoxious after he first handful of "Ya'll"s. I haven't seen many Barefoot Contessa shows, but her voice is like audio flurazepam and she does that thing (most hosts do) where she'll taste the food, dwell on it, and relate how good it is. We know it's going to be good, you're a professional on the Food Network. Giada DeLaurentiis is less irritating than most, though I find using Italian pronunciations of "naturalized" English words a bit pretentious.
Iron Chef is pretty entertaining fare. While I think the Japanese version used more unique secret ingredients ("Battle Live Eel"? Come on!), the American version presents its own challenge given the drive to be more creative with comparatively mundane ingredients. Of course, it might be that the uniqueness of the Japanese ingredients is more a matter of cultural differences. It's also neat to see how these ingredients are used in the hands of master craftsmen and women and the varying methods they employ.
Unwrapped, Ham on the Street, Diners, Drive-ins, and Dives, and The Secret Life of... are pretty good time wasters at work. Working midnights gives ample amounts of nothing to do but wait, and unfortunately there's a lot of nothing on TV! Those shows are well worth watching.