NEW YORK — “The Big Bang Theory” is one of the few television shows that can approach the NFL in viewership. CBS executives still didn’t hesitate to temporarily move TV’s top-rated comedy to a different night to make room for football.Already dominating Thursdays in prime time, CBS outbid its competitors when the league offered up games that had aired on NFL Network.“The highest priority for this corporation at that time was acquiring ‘Thursday Night Football,’” CBS Sports Chair Sean McManus said Monday.Thursdays conjure up memories of “Must See TV.” But viewers’ habits are now very different from the NBC heyday of “The Cosby Show” or “Friends.”So many more options abound: cable, Netflix, DVRs, on-demand. Viewers can fast-forward through ads or avoid them entirely.According to Nielsen, premiere episodes of “The Big Bang Theory” during the last TV season averaged a total of 23 million viewers over seven days — by that measure, even more than “Sunday Night Football.”But only 13.5 million watched live, compared with 20.9 million for the NFL games on NBC.On Thursdays, that’s especially problematic to advertisers, said Jack Myers, the chairman of media industry intelligence firm MyersBizNet.