I'm not sure about other Crown Princesses, Marengo, because I'm so far away and don't know a great deal about them. Like many Australians, I know a lot about the House of Windsor and Denmark's Royal Family, only because CP Mary was an Australian.
However, I did read enough in the press to know that the Crown Princess of Spain has been castigated in some circles; that the Crown Princess of The Netherlands suffered because of family connections; and that the Crown Princess of Norway was attacked because of her earlier life. All of these women were commoners, and, to my mind, were no better nor no worse than many aristocratic or royal-born women. Because I don't read Spanish, Dutch and Norwegian, I can only rely on second-hand reports of their difficulties and travails, with which, incidentally, I truly sympathised. This is not the case with Kate Middleton and Crown Princess Mary.
In sum, I think that I'll still stick with my hypothesis: that commoners who become the beloved of Crown Princes have an unduly unfair road to travel. I like them all and wish them every good thing, just as I do Kate Middleton, should she chose to marry William when he decides to wed.
As for CP Mary, I think that she's a winner, and that Denmark is lucky to have her as she obviouly loves their Crown Prince very much and is proving an exemplary mother to their future king.