Obviously preference should be given to actual leaders, but in order to come up with female rulers it may sometimes be necessary to use non-rulers who were influential in some way for that Civ. If you don't like Susan B. Anthony, fine, how about Eleanor Roosevelt? Eleanor Roosevelt, I believe, was the female ruler for America in CIV 2.
It's ridiculous that Civ 3 should be missing some of the fun things from Civ 2. I hope Civ 4 brings these things back... having multiple rulers makes the game more fun, especially if different rulers have differing traits. George Washington may bring militiaristic as a trait for America, whereas Thomas Jefferson might bring Commercial, and so on. Yes, it is alot of work to do the leaderheads so maybe there should just be two rulers per civ (one male and one female, just as in Civ 2) however the option should exist for players to customize their games by adding more rulers to choose from for their civ.