That's a very difficult question. - Edit 1
Before modification by Nate at 10/11/2011 02:23:31 AM
In no particular order:
Firefly
Breaking Bad
Farscape
Chuck
The Wire
Honorable Mention: The Shield, X-Files, Buffy, Wonderfalls, Doctor Who, Lost, Babylon 5, QI, and the first three seasons of 24.
Edit: the early seasons of House (say the first four) deserve honorable mention as well.
Firefly
Breaking Bad
Farscape
Chuck
The Wire
Honorable Mention: The Shield, X-Files, Buffy, Wonderfalls, Doctor Who, Lost, Babylon 5, QI, and the first three seasons of 24.
Edit: the early seasons of House (say the first four) deserve honorable mention as well.