i have never seen BB,so i cant comment on their chemistry,physics etc...Agreed, but I think the uniqueness comes from the built up of the character they are playing, because they both are free birds and have free hand to portary the character to perfection, they are not after proving anything , there on screen portrayal of the character is so so natural and gives a feeling of free birds in the sky, woh kehtay hai na " The sky is the limit" . The character was built up on FRIENDSHIP, COMPANIONSHIP first and then love came after, and that journey helped us to see the beautiful natural relationship which we see out in the real world too. They both had great people supporting them and the characters they are palying is not like any other in the TV right now. Both are brilliant .
Regarding Amir and Ragini, I was talking about Armaan and Bharti not Aamir and Ragini, and as I said that the character they were playing were not conventional, especially Bharti, she was not sure about her identity, and it was a difficult relationship to portray from her side, but Ragini did a brilliant job. The names you mentioned , unfortunaletly I heard of them but never saw there serials as I only watch Ragini,s serials, I am not into conventional TV serials , so pardon my ignorance.