Despite the powerhouse showings of its “ER,” “Friends” and “Will & Grace,” NBC retained its third-ranked position in last week’s Nielsen ratings. ABC is No. 1, thanks to the season return of “NYPD Blue” (ranked 19), “The American Music Awards” (23) and the debut of the reality series “The Mole” (30). ABC also has a little something called “Who Wants to Be a Millionaire” and “The Practice.” (The rating is the percentage of the nation’s estimated 102.2 million TV homes. Each ratings point represents 1,022,000 households.) The Top 10 for Jan. 8-14: