Back in the day, NBC was the king of network television. with hit shows like Seinfeld,Cheers,Frasier,Friends,Will & Grace,Wings,Family ties,The Cosby show,The A-Team,Magnum P.I.,Scrubs, and even My Name Is Earl. I know, some of these show aired in different periods of time. Point is, NBC had a lot of good shows.
Now,ever since they gave Conan O' Brien the Tonight Show at 12:05(not really the "tonight" show"),causing Conan to leave NBC, the network is now mediocre. At one point, it barely lead The CW for 4th place among network television.
This network is a shell of what it used to be. The only shows worth watching on it right now are The Office, Parks and Recreation,30 Rock,and Sunday Night Football. Most of these air on Thursday, so they still have an edge on Thursday night on primetime . They still have Leno and Fallon anchoring late night, so there is a little hope there.
NBC was the most watched network in America. Now, people only watch it on Thursday and Sunday.