There was a presidential news conference on 3/24/09, so the 8pm hour is omitted for all but the CW. I'm leaving out Fox altogether, since I don't have a breakdown on American Idol that would allow me to compare its 9:00 hour to the lowly House repeat last year... and that's a pretty meaningless comparison anyway.
(Lost vs. DWTS results) +18%
(The Forgotten vs. Primetime: What Would You Do?) -35%
(NCIS:LA (R) vs. NCIS) -53%
(The Good Wife (R) vs. The Mentalist) -64%
(90210 (R) vs. Reaper) -73%
(Melrose Place (R) vs. 90210 (R)) -50%