The broadcast premiere week started off with fireworks as several breakout hits emerged Monday and Tuesday — The Blacklist, Marvel’s Agents Of S.H.I.E.L.D., Sleepy Hollow — and some veteran series returned up year-to-year. But the euphoria subsided as the days went on and the week ended on a whimper, with a weak series launch (ABC’s Betrayal) and across-the-board ratings losses for everyone on Sunday. Here is a look at the four broadcast networks’ performance and a few Premiere Week takeaways:

Strong showing on Monday-Wednesday plus Sunday Night Football was enough for NBC to repeat as the No. 1 network during premiere week in adults 18-49 with its best premiere week rating in five years, 3.1, and the only net to post year-to-year increases in both 18-49 (up 7%) and total viewers (9.7 million, up 19%). What’s more, NBC widened its margin of victory from last year to 35%, the largest for any network in 16 years. And the bump came solely from the entertainment side as premiere week’s SNF was actually down 16% year-to-year (but still the top program of the week by a wide margin). With the exception of Revolution, NBC’s Monday-Wednesday returning shows were all up, led by The Voice. And NBC launched a solid new drama in The Blacklist, which posted the best 18-49 rating for a regular 10 PM drama (3.8) in the past year and the biggest viewer Live+3 increase ever, gaining 4.4 million persons in the first 3 days of DVR viewing. NBC’s problem spot once again is Thursday night where only one series, newbie The Michael J. Fox Show, broke the 2 demo rating threshold.

Related: The Big Story Of Premiere Week So Far: NBC

One swallow may not make a spring but one big hit can make a good fall. Look at ABC, which finished second in premiere week among adults 18-49 (2.3, up 5%), up from No. 4 last September, despite disappointing launches for Lucky 7 (1.3) and Betrayal (1.5), the lowest-rated series premieres so far this season with numbers that immediately open the cancellation door. But the network put all of its eggs in the Marvel basket and scored big with Marvel’s Agents Of S.H.I.E.L.D. which opened with a 4.7 18-49 rating, the top-rated new series and the biggest drama premiere in almost four years. The show also became a shining example of the new paradigm by almost doubling its live TV audience via repeat airing, DVR and online viewing in the first several days as more networks, led by Fox, are pushing multi-platform viewing stats. But there is a lot of reason for concern in the ABC executive suite as most of the network’s returning shows came back down, including flagships Modern Family and Grey’s Anatomy, and besides the S.H.I.E.L.D.-boosted The Goldbergs, the rest of the network’s new comedies, Trophy Wife and Back In The Game, had tepid debuts, and the upcoming Super Fun Night is already raising a red flag with the decision to scrap the pilot episode. In total viewers, ABC (8 million) was down 4%.

For the first time in years, CBS’ Monday night is vulnerable. The process actually started a couple of years ago when the network transplanted first The Big Bang Theory and then Two And A Half Men to Thursday. After a big first season, 2 Broke Girls has not grown into a formidable 9 PM anchor; none of the new Monday entries — Mom, Hostages and last night’s We Are Men — have impressed; and the series that is holding the night together, How I Met Your Mother, in its final season. The network’s biggest success came on Thursday, where The Big Bang Theory continues to defy gravity and posted series highs in Season 7 as the highest-rated entertainment program of premiere week (6.1 in 18-49, 20.44 million in Live plus same day) It also helped new comedy The Crazy Ones score the best opening for a comedy series so far this season with a 3.9 as CBS successfully expanded its Thursday comedy block to two hours. But most of the network’s returning shows were down and it finished premiere week tied with Fox for third place among adults 18-49 (2.2, down 8%) while maintaining the top position in total viewers (10.4 million, down 3%).

Fox (2.2, 6 million) posted the biggest year-to-year premiere week declines (15% in 18-49, 13% in total viewers). Some of the drops are tied to the fact that Fox launched most of its lineup a week early this year vs. during premiere week last season, so the network’s 2013 premiere week averages included second-week drops for many shows. But some of the losses are organic as The X Factor, Glee and the Sunday comedies are down double digits year to year. Fox’s Tuesday comedy block remains a work in progress, with newcomers Dads and Brooklyn Nine-Nine not providing ratings help and The Mindy Project trending down. But on the bright side, Fox has a solid new drama in Sleepy Hollow, which logged Fox’s biggest fall drama premiere in 6 years and is doing well three weeks in, both live and in DVR viewing where it is a big gainer. Fox also is making inroads on Fridays with a promising start for Masterchef Jr.

As we close the page of premiere week, here are a couple of lessons learned:

Lead-in still matters unless your title has Marvel in it. The Voice has successfully launched a third consecutive series, NBC’s The Blacklist, one of the breakouts this fall. (Last fall, The Voice served as a springboard for the biggest new fall series, Revolution, and the midseason before that it even made Smash look like a hit for a couple of months.) The Big Bang Theory buoyed CBS’ new Robin Williams comedy to a strong start and dominating victory over fellow newcomer The Michael J. Fox on NBC, which had a far weaker lead-in.

The Voice has successfully launched a third consecutive series, NBC’s The Blacklist, one of the breakouts this fall. (Last fall, The Voice served as a springboard for the biggest new fall series, Revolution, and the midseason before that it even made Smash look like a hit for a couple of months.) The Big Bang Theory buoyed CBS’ new Robin Williams comedy to a strong start and dominating victory over fellow newcomer The Michael J. Fox on NBC, which had a far weaker lead-in. Marketing (mostly) matters. The series that got the lion’s share of promotion, like S.H.I..E.L.D., Blacklist and Sleepy Hollow, opened well. Some, like ABC’s The Goldbergs reaped the benefits of both a big promotional push and strong lead-in (from S.H.I.E.L.D.), but the show’s solid early going may be deceptive — just look at last fall’s Go On on NBC, also propped up by a big lead-in from The Voice and wide marketing campaign that included a preview during the Summer Olympics. But when the show was left on its own, the wheels came off. And a massive launch campaign didn’t help new CBS’ Hostages.

The series that got the lion’s share of promotion, like S.H.I..E.L.D., Blacklist and Sleepy Hollow, opened well. Some, like ABC’s The Goldbergs reaped the benefits of both a big promotional push and strong lead-in (from S.H.I.E.L.D.), but the show’s solid early going may be deceptive — just look at last fall’s Go On on NBC, also propped up by a big lead-in from The Voice and wide marketing campaign that included a preview during the Summer Olympics. But when the show was left on its own, the wheels came off. And a massive launch campaign didn’t help new CBS’ Hostages. More than ever, Premiere Week performance is only a snapshot and doesn’t provide the full picture as the viewership for a number of shows is expected to double when DVR and online exposure is factored in. Still, for the most part, the snapshot is accurate in predicting which shows have a shot at staying on for the long run and which are heading into the proverbial bubble a week in.

Related: 2013-2014 Broadcast Season: The One Thing Each Network Must Pull Off To Claim Success

Here are the networks’ Premiere Week rankers:

Adults 18-49

Net… Premiere Week 2012… Premiere Week 2013…Diff

NBC…2.9…3.1…Up 7%

CBS…2.4…2.2…Down 8%

ABC…2.2…2.3…Up 5%

Fox…2.6…2.2…Down 15%

Total Viewers

Net…Premiere Week 2012…Premiere Week 2013…Diff

NBC…8.190 million …9.713 million…Up 19%

CBS…10.688 million…10.377 million…Down 3%

ABC…8.339 million …7.990 million…Down 4%

Fox…6.899 million …6.012 million…Down 13%