Why do so many people think that Pam and Mandy are the most beautiful? They are beautiful, but in a overly obvious way. And their nearly beach ball sized breasts (which I suspect are a big reason why so many people prefer them over the others) are overrated and actually kind of gross. I think that Katherine and Kristin are the most beautiful.
And just how would a marriage between JR and Mandy be realistic? They did not have a real relationship, just mostly sex. And just where were the common ground and interests? They were basically polar opposites in terms of personalities as well. If they had gotten married, we would have just had to watch even more of those boring bedroom and hot tub scenes. Although it might have been amusing to see them get kicked off of Southfork after everyone else in the house got sick of hearing Mandy say "OH, JR!" one too many times.
Pam and Bobby had nothing in common which was a positive; they came from entirely different backgrounds regarding upbringing, education, social class, and their interests were very different. The one thing they had in common which was a negative, and that was that Bobby's father hated Pam's father and vice versa. Yet look at how happy they were together and how much they loved each other. Many writers have even compared their love to one of the classic love stories of all time - Romeo and Juliet!
Ray and Donna had less in common than JR and Mandy and yet if things had gone as they were going in the "dream season"" they were on their way to adopting a boy and having a very happy marriage despite their many differences in practically every area imaginable
Many times relationships work because opposites attract. This may have been the case with Bobby and Pam and/or Ray and Donna. So of course JR and Mandy could have been a realistic relationship and a far more realistic choice than JR and Cally whose ages were just too far apart. Mandy had a very special quality and that was she was the only woman he ever had an affair with while married to Sue Ellen whom he actually fell in love with. There are plenty of examples throughout JR and Mndy's relationship of Mandy affecting JR in a much moe powerful and real way than any other woman who he had an affair with while married to Sue Ellen.
Was Mandy a homewrecker? She wasn't capable of ruining JR and Sue Ellen's marriage because their marriage was already ruined before JR met Mandy! In the first 7 or 8 seasons of Dallas JR and Sue Ellen's story was interesting: Will they work things out or will they be unable to do so? Around the time that Deborah Shelton started appearing on Dallas, they had had JR and Sue Ellen break up and get back together again (counting not just the first divorce but also Sue Ellen's constant state of flux regarding her choice of which Southfork bedroom she slept in) so many times that I found it impossible to care anymore because it as obvious that any time they got back together and Sue Ellen moved back int JR's bedroom, it was destined not to last. It got so repetitive as Dallas went to the well too many times with this ultimately repetitive and tiresome story. So having JR an Sue Ellen divorce a second time for good and then having JR marry Mandy would have brought much needed freshness to a very stale situation.
Mandy was the only woman of all the other possible next wives for JR who had such a powerful effect on JR that he became vulnerable and he was shown repeatedly in emotional pain over not being able to be in Mandy's presence and when he was with her he was shown looking ore happy and satisfied than we had ever seen him with any of the other potential next wives for JR including Cally herself.