LAST EDITED ON 01-16-08 AT 05:07 PM (EST)Actually, it was just under Season 4, not Season 5 (Season 5 wasn't as close) based on preliminary fast national ratings:
http://www.realitytvworld.com/news/ratings-american-idol-seventh-season-debuts-huge-but-down-bit-6401.php
Things could change a little when the Live + Same Day national data comes out later today, but I don't think there will be any way to do an absolutely pure apples-to-apples comparision of those numbers to all of the earlier seasons -- I think Nielsen only "created" the Live + Same Day national data that includes same-night DVR viewing a year or so ago (although DVR usage is certainly more commonplace now than then, I don't think Nielsen's same-day national numbers counted DVR usage before that). Then again, Idol is probably the type of show most folks are still going to want to watch live.
For whatever it's worth, there wasn't much difference between the Season 4's preliminary fast national ratings and the national numbers back in January 2005 -- prelim was 33.5 million viewers and a 14.0/33 in Adults 18-49 and national was 33.6 million and a 14.0/33 in Adults 18-49. Today's Reality TV World report used the earlier seasons' preliminary fast national numbers to keep all the comparisons the same.