While Fox easily won another Tuesday in key demos, it was CBS unscripted series “The Amazing Race” that impressed the most, hitting some series highs with the two-hour finale of its seventh edition, according to preliminary nationals from Nielsen.

From 9 to 11, “Amazing Race 7” (6.7 rating/16 share in adults 18-49, 16 million viewers overall) built with each half-hour, placing second in its first hour opposite Fox’s “House” (7.5/18 in 18-49, 18.9 million viewers overall) and then easily topping runner-up “Law & Order: Special Victims Unit” on NBC (4.8/12 in 18-49, 14 million viewers overall) in its second hour.

CBS was also a solid second in most categories at 8 with “NCIS” (3.0/9 in 18-49, 13.2 million viewers overall).

For Fox, “American Idol” (9.9/28 in 18-49, 24 million viewers overall) rolled as usual at 8, matching the other five broadcast nets combined in 18-49. And “House’s” perf at 9 was very strong, with the medical drama exhibiting the best-ever retention of its “Idol” lead-in.

Elsewhere, it wasn’t a great showing for comedies in the 9 o’clock hour, with ABC’s “According to Jim” (3.0/7 in 18-49, 8.0 million viewers overall) prevailing over NBC’s “Scrubs” at 9 (2.6/6 in 18-49, 6 million viewers overall) and a special second firstrun “Jim” at 9:30 (3.1/7 in 18-49, 8.2 million viewers overall) toppling NBC’s firstrun “Will & Grace” at 9:30 (2.4/6 in 18-49, 5.5 million viewers overall).

And at UPN, the season finale of “Veronica Mars” put up some of its better scores (1.2/3 in 18-49, 2.8 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 8.7/23; CBS, 5.5/14; NBC, 3.0/8; ABC, 2.4/6; WB, 1.9/5; UPN, 1.0/3.

In total viewers: Fox, 21.5 million; CBS, 15.1 million; NBC, 8.3 million; ABC, 6.6 million; WB, 4.4 million; UPN, 2.4 million.