The concluding hour of “24” achieved the drama’s best rating of the year Tuesday, teaming with “American Idol’s” final performance episode to give Fox a decisive ratings victory on the penultimate night of the season.

A winning Tuesday and the expected windfall for last night’s two-hour “Idol” finale has cemented Fox’s position as the No. 2 network in adults 18-49 for both the May sweep and the 2004-05 season.

And if roundoffs fall Fox’s way, its entertainment prexy Gail Berman said Wednesday, the net could finish just one-tenth behind NBC for the season — closer than last season’s two-tenths and its most competitive season to date. (Fox will finish with a 4.1 rating in 18-49, according to Nielsen, but NBC could be at either a 4.2 or 4.3 depending on how it fared Wednesday).

“This is an extraordinary moment in our network’s history,” Berman told reporters on a conference call.

Net got to this point thanks in large part to “American Idol,” whose Tuesday edition averaged 25.8 million viewers this season to edge out CBS drama “CSI” as the season’s most-watched program overall. The two nights of “Idol” also finished 1-2 in the season rankings among adults 18-49.

Berman dismissed the notion that Fox is overplaying its “Idol” hand, even though at 19.5% of its May sweep sked (firstruns only), “Idol” is more important to the net than even “Who Wants to Be a Millionaire” was for ABC at its peak in May 2000 (19.3%).

“I do believe we’ve shown tremendous restraint in deciding to utilize this as a once-a-year event,” Berman said. “We saw 17% growth in this show, and that says a tremendous amount about our scheduling decisions.”

Another big part of Fox’s season was sudser “The OC,” which ranks as the No. 1 new drama among viewers under 35 and the top new scripted program among teens. It helped the net win the season by 71% in viewers 12-17 — the most dominant teen victory in Nielsen’s record book.

Berman also gave nods to a pair of short-run unscripted programs, “The Simple Life” and “My Big Fat Obnoxious Fiance,” that she said represent “a new hybrid form of comedy reality.” Both shows finished among the season’s top 20 skeins in 18-49.

And “The Swan” edged out ABC’s “Extreme Makeover” as the season’s No. 1 surgery skein in 18-49.

On Tuesday, “24” hit season highs (5.7/14 in 18-49, 12.31 million viewers overall) and easily led its time period. It came out of another dominant perf by “American Idol” (10.6/30 in 18-49, 25.13m), which beat the other five broadcast nets combined in 18-49.

Although “American Idol” continues to outperform last year’s boffo numbers for the season, the show has fallen behind its scorching 18-49 pace of last May. Tuesday, for example, was down 5% in the demo from last year’s corresponding seg in 18-49 (11.2/31).

Second-place ABC enjoyed its best Tuesday since February thanks to the season finale of “According to Jim” at 9:30 (4.2/10 in 18-49, 9.84m) and the best numbers of the month for quizzer “Super Millionaire” (slot-leading 4.1/11 in 18-49, 11.36m).

Over on TNT, Game 3 of the Lakers-Timberwolves series drew a big 8.09 million viewers, making it the most-watched NBA Playoff game in cable history.