“American Idol” and a trio of young dramas lifted Fox to a primetime ratings victory last week in a frame that saw many of the top shows on competing networks air repeats.

While “Idol” continues to track at well below last year’s start, it still finished at the top of the ratings charts for the week. Also for the net, “Alcatraz” held up well in its second outing, “Idol” helped Kiefer Sutherland drama “Touch” open nicely on Wednesday, and “Bones” spinoff “The Finder” hit a high on Thursday.

It was also a big week for “The Big Bang Theory,” as the CBS comedy racked up its best Thursday numbers to date and again beat “Idol” head-to-head in demos. Also, numerous repeats of the show lifted TBS to the top spot in young-adult rankings among cablers.

Overall, according to Nielsen, Fox led in adults 18-49 (3.0 rating/8 share) — well ahead of CBS (2.0/6), NBC (1.8/5), ABC (1.6/4) and Univision (1.3/3). Net also rolled in adults 25-54 (3.4/8 to 2.8/7 for CBS) while CBS led in total viewers (9.3 million to 8 million for Fox).

The Wednesday hour of “American Idol” was the week’s No. 1 show in 18-49 (6.5/18) and total viewers (19.67 million) — down 8% from its opening hour one week earlier and off 24% from the comparable hour a year ago.

“Idol” led into a special preview of “Touch” that performed well (3.9/10, 12.01m) in advance of its March 19 premiere, and “The Finder” discovered its best scores in its three airings (2.8/7, 8.44m), taking advantage of drama repeats on the competish.

Prison drama “Alcatraz” (3.0/7, 9.03m) meshed well with “House” (3.1/8, 8.76m), retaining 94% of its 18-49 premiere rating; it joins “Once Upon a Time” and “Terra Nova” as the season’s only rookie dramas to earn a demo score of 3 or higher in their second outings.

On the weekend, Fox got a big boost Saturday from UFC action (2.4/8, 4.66m), roughly matching the combined demos on the night for ABC, CBS and NBC. Fox’s Sunday lineup looked sluggish, with the third week of “Napoleon Dynamite” (2.1/5, 4.42m) softish between “The Simpsons” (2.4/6, 5.03m) and “Family Guy” (3.1/7, 5.92m).

CBS stepped up on Wednesday with “Criminal Minds” (3.7/9, 13.81m) and “CSI” (3.4/9, 14.26m); the latter, in the swan-song seg for original cast member Marg Helgenberger, earned the best numbers for a regular 10 p.m. drama on any net and night this season.

“The Big Bang Theory” (5.5/16 in 18-49, 16.13m) toppled Fox’s “Idol” head-to-head (5.5 vs. 4.9 in 18-49 and 6.9 vs. 6.0 in 25-54), hitting its best scores since moving to Thursday. And lead-out laffer “Rob” held steady in its third week (3.5/9, 11.50m) — a good number, especially up against “Idol.”NBC was quiet until Sunday, when the NFL’s Pro Bowl won the night (4.3/11 in 18-49, 12.50m), though down year to year. Earlier, the net’s Wednesday comedy hour of “Whitney” (1.4/4, 4.40m) and “Are You There, Chelsea” (1.4/4, 3.80m) dipped further in their third week together, and “Chuck” ended its run Friday with a season high (1.3/4, 4.31m).

ABC was paced by “Once Upon a Time” (3.5/8, 10.91m), Sunday’s No. 1 series in demos. Also, “The Bachelor” hit some season highs (2.7/7, 8.30m), and Friday’s lineup of “Shark Tank” (1.5/5, 5.44m), “Primetime: What Would You Do?” (1.7/5, 5.17m) and “20/20” (1.5/4, 5.73m) looked good in their second week together.

In cable, “Jersey Shore” (3.8/10, 6.53m) dominated its Thursday hour and ranked sixth for the week in 18-49.

“Kourtney and Kim Take New York” wrapped its season Sunday with some of the best scores ever for an E! series (2.6/6, 4.48m), leading all of television in its slot among women 25-54 (3.5/6).

It was a good week for Bravo’s “Real Housewives,” as Monday’s Beverly Hills edition (1.6/4 in 18-49, 3.03m) was cable’s No. 1 show of the night in women 25-54 (2.5/6). And Sunday’s Atlanta version (2.1/5, 3.95m) racked up the second largest aud for any episode in “RH” history.

Discovery again shined on Friday with “Gold Rush” (1.7/5, 4.24m) leading into “Bering Sea Gold” (1.4/4, 3.66m), which saw the net’s highest-rated series launch to date; no shows on television that night drew more young men.

ABC Family’s “Pretty Little Liars” (1.4/4, 3.17m) was the week’s No. 1 cable drama in 18-49; on Thursday, CNN’s Republican debate drew 5.36 million viewers, the net’s largest aud for this election cycle; and the SAG Awards on Sunday drew 5.13 million viewers on TNT and TBS, up a bit from last year (5.01m).