1. Answer: It depends on everyone's taste and these rankings change all the time. According to RankMyPorn, at the moment, the top ranked Straight Female Pornstars in the world are: August Ames, Rebeca Linares, Shawna Lenee, Quinn Wilde, Pepper Hart, Cherie Deville, Zaya Cassidy, Anya Ivy, AJ Applegate, Ann Marie Rios, but these will change based on what people vote.
2. Answer: It changes. You can see the latest rankings on RankMyPorn.com and also vote on it for free.