I'm not quite sure I understand the parameters of the question. All that is required for porn is being physically attractive and being willing to do it. If by "attitude" you are trying to infer how well they would "perform", I'd say that is very hard to do. The celebs who show more skin may seem "sluttier" but that doesn't mean they'd perform better.
My only answer is that in terms of physical type, porn leans toward curvy figures, larger breasts (esp. natural), and large round bubble butts. Three names off the top of my head which fit that bill are Sofia Vergara, Salma Hayek, and Kelly Brook. All three have classic all natural curvaceous bodies which are of the type that is highly prized in porn. Someone like Alicia Silverstone or Miley Cyrus may be considered attractive by many people, but slim physique, small ass, small breasts is more of a niche in porn. I feel the same way about Emma Watson and Selena Gomez, two of the prettiest girls on the planet right now. Either could be successful in porn, but neither has the ideal body type.