Just about every year (even the famous 2007 FTW tour) we see teams with losing records giving good teams a game. Just in 2007 alone we had BAL, PHI, and I'm sure there was a tougher divisional game at some point late in the season thrown in, although I don't remember specifically who it was against.
Even last year we had JAX, MIA, BUF etc who we struggled with for awhile, yet still went to the AFCCG and had a shot at the SB. I'd have hated if we couldn't have played for the SB in 2004 when we lost on Xmas eve to a 2-13 Miami team. Some days are better than others.
You can only play who is on your schedule, and even though Northwestern is deemed as poor now, they were ranked #16 at the time OSU played them. They were actually pumped up and played tough at home on Sat night in front of national TV. Of course now people are claiming that it should've been a walk in the park, but it doesn't always work like that.
In my opinion, if you're in a major conference and you beat all of your opponents, you're going to have a pretty good shot at competing for a national title. I will admit that the Big ten wasn't too good this year, but neither was FSU's ACC either, and yet you don't hear too much about that fact.