I tend to think that each TV show will be interresting, as you'll learn each time a different semantic field
. Depending where the series takes place, and when, who are the people involved and the narrative... or simply, which public the show is written for!
Star trek will allow you to learn a lot of technical terms (along with tons of techno babble you won't need elsewhere, until some nerd Trekkie scientists name their breakthrough from it)... Historical shows like The Tudors (or more recently The crown) have a more formal sentences (though accessible), and cop show like the shield, obviously, will be interresting to hear about police things as about different tribe stuff (that's true for prison flicks, as well). But I think - probably falsely - that the best thing one could do to improve his skills in a foreign language is... humor. You probably won't learn that much vocabulary, but you'll get much from rhythm, speed, sentences, tropes and culture. People around the world don't necessarily laugh to the same things simply because they were not raised the same way, with the same cultural references, and humor is often one of the thing the more difficult to translate. Try to watch a comic show you know well overdubbed, and you'll probably discover it again. It's a good thing to do with all genre, as well.
If you're already there, try to forget the French subtitles and go for the English ones. That way, you won't be perturbed by the differences between the two, you'll concentrate on watching and hearing. You can read when there is a word you don't recognise, or simply one that don't know.