So when was the Golden Age of Television? Let's take a look***:
- Buffy the Vampire Slayer (1997-2003)
- Futurama (original run) (1999-2003)
- Angel (1999-2004)
- The West Wing (1999-2006)
- The Sopranos (1999-2007)
- The Wire (2002-2008)
- Arrested Development (2003-2006)
- Battlestar Galactica (2004-2009)
- Veronica Mars (2004-2007)
- Deadwood (2004-2006)
- Lost (2004-2010)
- The Office (2005-present)
- Heroes (2006-2010)
- Mad Men (2007-present)
So I would offer that the sweet spot here is from about 2003 until about 2006, maybe 2007. After that these shows were either no longer on the air or else noticeably grasping at straws.
Why am I wrong?
*** Not on this list: The Daily Show, the Colbert Report, and Late Night with Conan O'Brien, all of which were making terrific television at the same time period. For that matter, there were also a number of great reality shows on at the same time. It's just easier for our purposes if we stick with scripted shows.