This poses a really good question. It's been thrown around lately that we're in somewhat of a golden age of television, with the sheer quality of some of the television that's being produced. What I wonder is if it's just now that great shows are being allowed to flourish, rather than being cancelled instantly by network executives that don't "get" the shows, or if the shows themselves are of any better quality. I'd say right now, we have more quality original programming coming out on TV (and now netflix) than I'd say we have had in quite a while. Does it just happen to be that good shows are being made now, or that they're being allowed to thrive? Or are audiences just so sick of bad TV that they are flocking to better shows?
I think it might be a combination of a few things. I'm willing to be corrected, of course:
-The lack of ingenuity coming from the big wigs, like NBC, CBS, etc. They've had the odd one that was well received like Heroes or Lost, but many of them were the same thing all the time. How many flipping CSI shows were there? And I wasn't crazy about House because it was ridiculously formulaic (despite great performance by the guy that played House). The other networks like AMC and HBO are willing to take a few more risks, like Dexter. That's the kind of show I wouldn't have even thought possible ten years ago.
-The advent of DVD and especially Netflix has boosted interest in TV shows. Before, it was incredibly hard to catch up on shows or check out new ones without catching them on TV or not-so-legally getting them. Now, there more avenues to watch all of a series (legally and illegally). DVD and Netflix also boosts sales for shows, too. I imagine some struggling shows make a good chunk of money back on their DVD sales. Hell, even though Firefly was cancelled, it got a frigging movie because of its DVD sales.
-The popularity of nerd culture has boosted the potential for very different kinds of shows, like Walking Dead and Game of Thrones. Even Heroes, Battlestar, or Lost might not've been considered only a few years before. Sci-fi and fantasy was always a niche market, but now it's hitting a much larger general audience.
-Big name actors are starting to catch on to TV's popularity, which I think started with Kiefer Sutherland coming on board for 24.