The show drew 21.4 million in the 2012 season, compared with NCIS's 18.5 million.
American Idol or another show could surpass Sunday Night Football's average viewership in the spring, but experts say that seems unlikely.
It's a big win for the Comcast Corp.-owned TV network and confirms the NFL's prime-time broadcast-TV dominance even as TV viewers have enjoyed an explosion of entertainment options: hundreds of cable channels, Hulu, and Netflix.
Last year, the 2011-12 TV season "marked the first time in history of TV, dating back to the 1950s, that a live sporting event was the highest-rated show in prime time, and it looks like that will happen this year unless something unforeseen happens," said Brad Adgate, senior vice president for research at Horizon Media. This year is the 2012-13 TV season.
Monday Night Football, meanwhile, now on ESPN, remains the top-rated show on cable, with an average viewership of 12.8 million this year, down from 14.7 million in the 2010-11 season and 17.1 million when it aired on ABC in 2002-03 season.
ESPN spokesman Bill Hofheimer said Monday Night Football's viewership this fall seemed to be affected by "lopsided games," Hurricane Sandy, and a Monday night presidential debate. Its season opener was a blowout, with the Baltimore Ravens beating the Cincinnati Bengals, 44-13.
Hofheimer said that Monday Night Football was the most-watched cable show for the seventh year and that it won in the male demographics on both broadcast- and cable-TV.
NBC has benefited from "flexible scheduling" that lets the network substitute a more attractive NFL game for a potentially uncompetitive match-up on some Sunday nights - though Fox and CBS retain some blocking rights to the switch. NBC, for example, replaced its San Diego Chargers vs. New York Jets match-up in the season's 16th week with the Seattle Seahawks vs. the San Francisco 49ers.
Some industry analysts also say the NFL has scheduled more competitive games on NBC because its economics are based solely on viewership and ratings related to advertising, while ESPN earns most of its revenue through cable-subscriber fees.
The 21.4 million average viewers for Sunday Night Football was based on 17 Sunday games, along with a Wednesday night season opener, and a Thanksgiving game, which are included in NBC's NFL package.
"There are not that many things that reach 20 million people," Mark Lazarus, chairman of NBC Sports Group, said in a recent interview. "There are very few communal viewing opportunities in today's TV," he said, adding, "we strive to make every night feel like it's a big event."
Sunday Night Football was reportedly unprofitable under former owner General Electric, but Lazarus said the show would be profitable this year. Comcast bought a controlling 51 percent share of NBCUniversal in early 2011.
NBC charged an average of $575,000 for a 30-second advertisement on Sunday Night Football, more than double the $239,866 for a 30-second spot on NBC's second-highest-rated prime-time show, The Voice, according to the trade publication Advertising Age.
NBC launched its Sunday night franchise on Sept. 10, 2006, with a game featuring the brothers Peyton and Eli Manning.
In that debut season on broadcast TV, Sunday Night Football competed with newly popular reality shows and high-rated Hollywood-scripted entertainment.
It finished ninth in average viewership among all prime-time shows, behind shows such as American Idol, Dancing with the Stars, CSI, G rey's Anatomy, House, and Desperate Housewives. Some of those shows aired more than one night and, in fact, beat Sunday Night Football twice.
The next year, Sunday Night Football rose to No. 8 and stayed there for two years. Desperate Housewives and House fell behind Sunday Night Football in viewership, but other shows, NCIS and the Mentalist, rose ahead of it.
Sunday Night Football ranked fourth in the 2009-10 TV season behind American Idol and Dancing with the Stars. There were two Idol shows that year with higher average viewership.
In 2010-11, Sunday Night Football placed third behind two American Idol shows and then jumped to first during the 2011-12 season.
"There is not a new compelling hit that will get 20 million viewers an episode," Adgate said, echoing the comment by NBC's Lazarus. " Idol is the last one."
Contact Bob Fernandez at 215-854-5897 or firstname.lastname@example.org.