The TV networks’ ratings for "premiere week," when many returning shows have their first new episodes of the season, were up over last year’s performance. As Reuters reports:

CBS on Tuesday claimed victory as the most watched television network in prime-time during last week’s fall premieres, but more people tuned in overall than last year, giving each network victories to tout.

Led by crime dramas "CSI," "CSI: Miami," and "Without a Trace," CBS drew an average of slightly over 13 million viewers a night, up 2 percent from 2005, compared to second-place ABC’s 12.3 million viewers, according to Nielsen Media Research.

But ABC scored the week’s No. 1 show with the premiere of hospital drama "Grey’s Anatomy," which pulled in 25 million viewers on its Thursday night premiere to "CSI’s" 23 million. . . .

"It was a solid premiere week, and I don’t think there were any real ratings disasters," said Nicholas Fonseca, staff editor for Entertainment Weekly magazine. "I think every network has something to be happy with."

But there were no big winners either, as happened in 2004 with ABC hits "Lost" and "Desperate Housewives," making industry watchers anxious to see whether viewership will slip in coming weeks.

NBC showed improvement over last year also. And although it was reported earlier that Fox’s ratings had slipped by 20-35 percent with the coming of the new season, the network bounced back during premiere week:

Fox also improved during the week, led by dramas "House" and "Prison Break." Its viewership was up 16 percent among all viewers and 11 percent in adults 18-49. . . . Fox also awaits the mid-season premieres of "American Idol" and drama "24," which are among TV’s top-rated shows.

Whether this increase in viewership will be sustained is the big question, of course. Many of the new shows seem to be very similar to one another, and one suspects that there will be a major shake-out down the line, as there are few shows with obvious hit potential.

Probably the strongest candidates for success so far are NBC’s smart soap opera Studio 60 on Sunset Strip, Fox’s sex-heavy but funny comedy ‘Til Death, and CBS’s Shark, with James Woods in another of the network’s strong lineup of pro-law and order shows.

Most likely to be cancelled first: Fox’s amusing Happy Hour, which has drawn about one-fourth as many viewers as timeslot competitor Survivor: Cook Island on CBS. The network has placed the show on a production hiatus and replaced it with reruns of ‘Til Death, which benefits from the relative star power of Brad Garrett (Everybody Loves Raymond).

Being replaced, even if only "temporarily," by another show is bad enough, and being replaced by a rerun is even worse. But being replaced by a rerun of a brand-new show is a real disaster.