An average of 23 million viewers tuned in to NBC to watch the first Sunday Night Football game (actually played on Sunday) of the season, which, if the overnight numbers hold up, would make it the most-watched SNF telecast ever -- up 3 percent over last year's record for a season opener. Actually, because overnight ratings for live events are generally lower than the final figures, it's a safe bet that the numbers for The Game between the Dallas Cowboys and the New York Jets will go even higher, landing in the vicinity of 25 million. A two-hour documentary on CBS, 9/11 10 Years Later , which aired opposite the game, also drew surprisingly high ratings, averaging 12.6 million viewers. Meanwhile, an eight-minute preview of Simon Cowell's The X-Factor , broadcast at the end of The O.T. , clearly boosted ratings for Fox, which went from 7.5 million viewers during the 7 00 half hour to an average of 10.4 million during the 7 30 p.m. half hour.