Got to break it down in different eras. Could easily add more to the older years (MASH, Welcome Back Kotter, Hawaii Five 0, Happy Days, yada yada yada). Shows were so much better 20-30 years ago.
Current (2000 and beyond):
The Shield
Sopranos
CSI
Recent (80's & 90's):
Seinfeld
Taxi
X-Files
Old School (60's & 70's):
All in the Family
Sanford and Son
Hogans Heroes