Based on S&P+, 2003 USC, 2007 USC, 2008 USC, 2009 Florida and 2010 Alabama are the 5 teams to finish #1 and not win the NC. None of those are options, so I voted "Other".
I'm trying to distinguish between 2007 and 2008 USC. But I do remember 2007 was an absolute mess of a year, and USC still couldn't take advantage, while both Oklahoma and Florida were really good in 2008. So I'll say 2008 USC was the best, and they didn't even play for it.