I'm not that surprised that we still rank fairly highly.  Those teams from 2000-2003 included some stout defenses, and NFL teams loved the linebackers and defensive backs we had.

On top of that, our decline post-2003 hasn't been as much attributable to a drop in talent as it has been to a decline in coaching ability, specifically assistant-coaching ability.  The reason we declined in 2004 and 2005 wasn't because Bill Snyder suddenly became a bad coach; it was more because we didn't have Bob and Mike Stoops, Brent Venables, Bret Bielema, Jim Leavitt and others helping out.

One quick note on the lack of domination by the Southern schools; until its title in 2000, OU was in a period of serious decline, and it took a few years before the talent level was fully restocked.  Texas likewise was mired in a serious downturn in the late 1990s, at least by its standards.  It probably wasn't until at least 2002 or so that it was fully reestablished and restocked with top-flight talent.