While upset over the deaths, I found Sun and Jin's death together very much in the vain of Korean dramas. Just when you think there's going to be a happy ending...there isn't. And after my kneejerk reaction, I love that the writer's had the guts to do something like that.
Now if they touch Bernard and Rose...they's be askin' for trouble.
Depends on the drama...Dae Jang Geum/Jewel in the Palace had a happy ending --yet the characters never even kiss on screen!
With Bernard & Rose, and of course Penny & Desmond...that's just way too many couples living happily ever after (if Bernard & Rose weren't Adam & EVe), so why Jin & Sun get the short end of the stick.
Also, it's also ironic that after this big fight to find each other, they lose each other forever. If Sun had just let Jin go (i.e. not come to the Isalnd in the first place), they all might be re0united as a family. We'll see...
My prediction is that the flashsideways will end with all of them uniting and going back in time and starting a third reality...where MIB loses, and "happily ever after."