NEW YORK -- NBC has emerged as the big winner after one week of the new television season, with hopes that it won't all come crashing down the way it did last year.

Each of the four biggest broadcast networks had some carefully nurtured initial successes. But NBC was alone in seeing more prime-time viewers than it had during the same week in 2012, and the increase was 19 percent. Among the 18-to-49-year-old demographic that many advertisers seek, NBC had the widest first-week margin of victory in 16 years, the Nielsen ratings company said.

The success of "The Voice," which fills two-hour chunks of NBC's schedule on Monday night and Tuesday night, is a major factor. Monday's show last week reached nearly 15 million viewers, with slightly fewer on Tuesday. Meanwhile, Simon Cowell's "The X-Factor" on Fox finished below 8 million viewers for both of its nights last week.

NBC's James Spader drama, "The Blacklist," started strong with 12.6 million viewers last week, Nielsen said.

NBC has its skeptics. Michael J. Fox's well-publicized new sitcom gave NBC a pulse on Thursday night, but it still ranked No. 43 among the week's shows. The network collapsed in mid-winter last season following a strong start when pro football ended and "The Voice" went on hiatus.

"Their season could turn out a lot like last season, but they're starting higher," said Bill Gorman, co-founder of the website TV By the Numbers.

One key difference for NBC is it will broadcast the Winter Olympics this year.

Despite NBC's gains, CBS maintained its status as the most-watched network overall. CBS succeeded in giving a strong start to "The Crazy Ones," Robin Williams' new sitcom, which finished among Nielsen's top 10 shows. Williams' show was helped by airing directly after "The Big Bang Theory," which opened its seventh season with the largest audience it has ever had.

CBS averaged 10.4 million viewers in prime time for the week. NBC had 9.7 million, ABC had 8 million, Fox had 6 million.

One concern for CBS has to be its formerly dominant Monday night lineup. "2 Broke Girls" was given the evening's showcase time slot at 9 p.m., yet finished No. 34 among broadcast shows last week, Nielsen said.

ABC's adventure series "Marvel's Agents of S.H.I.E.L.D." was the network's most-watched scripted show last week, its audience bigger than that for "Modern Family."

In terms of new shows, that was ABC's highlight.

New ABC series "Lucky 7" and "Betrayal" have the look of shows that won't last long.

Fox had the steepest decline year-to-year, losing nearly 1 million viewers.

ESPN was the most-watched cable network last week, averaging 3.1 million viewers in prime time.

For the week of Sept. 23-29, the top 10 shows, their networks and viewerships (in millions):

1. NFL Football: New England at Atlanta (NBC), 20.49

2. "The Big Bang Theory" (Thursday, 8:31 p.m.) (CBS), 20.44

3. "NCIS" (CBS), 20.0

4. "The Big Bang Theory" (CBS), 18.9

5. "NCIS: Los Angeles" (CBS), 16.3

6. "The Crazy Ones" (CBS), 15.5

7. "Sunday Night NFL Pre-Kick" (NBC), 15.2

8. "The Voice" (Monday) (NBC), 14.9

9. "The Voice" (Tuesday) (NBC), 14.3

10. NFL Football: Oakland at Denver (ESPN), 13.9