Mathematically, they are of precisely equal importance. When doing the calculation, it is simply Cd . A, they are multiplied together. A 10% reduction in one has precisely the same effect as a 10% reduction in the other.
You may be referring to that if you want to have two people seated beside each other in a seating position that normal people would find to be acceptable, there is a point below which the frontal area is not readily reducible, and hence the frontal area of most modern cars is in the same range, so it appears to have little effect. But rest assured that the effect of frontal area is every bit as important as that of drag coefficient - you just can't do much about it below a certain minimum that people are willing to tolerate.
For an example of an unconventional approach to frontal area reduction, see VW XL1.
Interesting table, though. Shows why the old Honda CRX was an ecomodder's dream. Small frontal area and good drag coefficient. It comes close to the original Insight, which has the smallest Cd.A that I see in that table for a production car ... There are quite a few Honda and Acura models that are among the best.