‘The Simpsons’ Jumps Into the Top 10 : Ratings: A rerun of Fox’s animated series defeats NBC’s ‘The Cosby Show.’ The two comedies will square off for real next season.

Homer Simpson’s environmental crusade last Sunday propelled the Fox animated series “The Simpsons” to the young network’s first top-10 finish in the weekly ratings, according to figures released Tuesday by the A.C. Nielsen Co.

Seen in nearly 14.5 million homes nationwide, “The Simpsons” tied ABC’s “America’s Funniest Home Videos” for fourth among last week’s 87 prime-time shows, trailing only “Cheers” on NBC, “Roseanne” on ABC and NBC’s premiere of “Seinfeld,” which held fast to most of the people who watched the show ahead of it, “Cheers.” “Seinfeld” was the only first-run program to finish in the top 50 last week.

Fox bragged Tuesday that “The Simpsons” was seen in about 370,000 more homes than NBC’s “The Cosby Show,” which managed only a tie for eighth in its Thursday time period. In perhaps the boldest move of the upcoming fall season, Fox plans to move “The Simpsons” to Thursdays to compete directly with “Cosby,” this past season’s No. 2-rated show behind “Roseanne” and the unchallenged ratings king of the 1980s.

But last week was the first week of summer schedules, and the surfeit of reruns on all four networks and the warm weather in much of the country combined to reduce the audience for nearly all network series. The three major networks together attracted only 55% of the prime-time viewers--about 10 points below their average during the official season between September and April.

Last Thursday’s “Cosby” rerun, for example, was seen in about 7 million fewer homes than the show averaged for the 1989-90 season.

And an original episode of “The Simpsons” during the first week of last month’s sweeps period actually scored a higher rating than the repeat that aired last Sunday but it ranked only 13th that week because the other networks’ ratings were so much higher.

In other words, “The Simpsons” ranked higher last week because it lost less of its regular audience than most other shows.

That was also true for several other of Fox’s Sunday-night series. Following “The Simpsons,” a repeat of “Married . . . With Children” finished 11th for the week, and a new episode of “In Living Color” zoomed up to 19th.

In Los Angeles, Fox soared even higher as these three shows gave KTTV Channel 11 three of the four top-rated series of the week.

While most analysts believe that “The Simpsons” will make at least a dent in NBC’s longtime stranglehold on the Thursday-night audience this fall when Fox attempts to use it to launch a new night of programming, some have questioned the wisdom of breaking up Fox’s own Sunday juggernaut. They question whether the other series can perform as well without the lead-in of “The Simpsons.”

For example, “In Living Color,” the caustic and sometimes risque new series from Keenan Ivory Wayans, could get crushed when Fox moves it from its cushy time period following “The Simpsons” and “Married . . . With Children” to 8 p.m. on Sundays against ABC’s own ratings phenomenon, “America’s Funniest Home Videos.” Though Fox has proven it can compete with the Big Three with a few shows in a few time periods, many of the network’s programs have floundered. Last week, for example, Fox also took credit for five of the six least-watched prime-time programs.

NBC won the week with a 10.9 rating and 20% share of the audience. ABC was second with a 10.2 and 19 share, while CBS trailed with a 8.9 and 16 share. Fox averaged a 6.2 rating for its 10 hours of prime-time programming on Monday, Wednesday, Saturday and Sunday. Each rating point represents 921,000 households.

CBS’ telecast of the Tony Awards,” honoring Broadway’s best, scored a lowly 7.6 rating and 13 share on Sunday, crushed by “Revealing Evidence,” a first-run TV-movie on NBC that garnered a 14.5 rating and 24 share.

NBA playoff games--one between Chicago and Detroit and two others featuring Portland against Phoenix--limped to 40th, 48th and 53rd places respectively.

‘CHEERS’ ON TOP--”Cheers,” “Roseanne” and “Seinfeld” lead the ratings. The full list is on Page 9