The Big Bang Theory ran a rerun for May 24, 2012. This episode still got the most viewers of all TV shows for the night for every time slot, not just its own. It got about 8.3 million viewers.
In terms of the 18-to-49 demographic, The Big Bang Theory was 2nd in its time slot, but that was also second for the whole night. Its 2.3 rating was only behind So You Think You Can Dance’s 2.4. And that was SYTYCD’s season premiere. It also beat out the Duets season and series premiere in both categories (demo and viewers).
All of the other shows on May 24th got a 1.7 or lower rating in the demographic. Only reruns of Person of Interest and The Mentalist came close in total viewers, with about 7.8 million viewers each.
Keep in mind that these are preliminary broadcast numbers, but The Big Bang Theory was easily the #1 show for total viewers and easily in the Top 2 in the demographic. So the key ratings will not change.