There's a difference in ranking how "good" you believe teams are and how "deserving" you believe teams are.
For example, if I were ranking Iowa versus Alabama, I think Iowa "deserves" to be ranked higher as they have not lost a game yet this season. At the same time, I believe Alabama is the better team (i.e., if they were to play next week on a neutral field, I would expect Alabama to win).
So when I say that I think that Iowa is only about the 15th "best" team in college football, that does not mean I don't think they should be ranked in the top 10 or in the top 4 if they happen to be 13-0.