ABC’s unscripted skein “American Inventor” opened well Thursday, lifting the Alphabet to its first in-season primetime ratings victory on the night (excluding sports) in more than three years.

According to preliminary nationals from Nielsen, “American Inventor,” from creator Simon Cowell, averaged a 5.4 rating/15 share in adults 18-49 and 14.2 million viewers overall from 8 to 10, growing with each half-hour. It gave ABC its strongest 18-49 delivery with series programming in the time period since November 2000. That led into an above average “Primetime” (3.3/9 in 18-49, 8.7 million viewers overall), although it remained third for the hour.

CBS, which preempted its top-rated lineup for college basketball, figures to come in second or third for the night in 18-49, although not too far behind ABC. Its prelim primetime average of 4/11is expected to rise in the nationals. In Nielsen’s metered-market household overnights, the Eye’s entire opening day of the NCAA men’s basketball tourney averaged a 4.9 rating/10 share — up slightly from last year’s 4.8/10 and the third best score in the past 13 years.

NBC had the night’s top show in 18-49 in “ER” (5.8/15 in 18-49, 14.1 million viewers overall), although the medical drama — even without competition from CBS’ “Without a Trace” — was in record low territory. Rookie comedy “My Name is Earl” also hit a low at 9 (4.5/12 in 18-49, 10.6 million viewers overall), likely affected by its weak lead-in from “Four Kings” (2.9/8 in 18-49, 6.9 million viewers overall). At 9:30, “The Office” (4.2/11 in 18-49, 8.9 million viewers overall) retained most of its “Earl” lead-in.

Fox was on the low side with its lineup of “That ’70s Show” (2.4/7 in 18-49, 5.5 million viewers overall), the timeslot premiere of “The Loop” (2/6 in 18-49, 4.8 million viewers overall) and “The OC” (2.4/6 in 18-49, 5.5 million viewers overall).

Preliminary 18-49 averages for the night: ABC, 4.7/13; NBC, 4.5/12; CBS, 4/11; Fox, 2.3/6; WB, 1.1/3; UPN, 0.9/2.

In total viewers: ABC, 12.4 million; CBS, 10.8 million; NBC, 10.6 million; Fox, 5.3 million; WB, 2.7 million; UPN, 2.2 million.