Even more pathetic than you realized:
In 1989, there were 106 Division 1A (now called FBS) teams. A total of 582 games were played between those teams, including 18 bowl games. 52 of the total games (8.9 percent, or about 1 in 11) were played between teams ranked in the Associated Press final top-25.
In 2009, 120 FBS teams played a total of 714 games against one another, including 34 bowl games. Only 38 of the total games (5.3 percent, or about 1 in 20) were played between Associated Press final top-25 teams.
More, with pictures and stuff, at BCF Toys. (T/F/J: GTP)