This is just my opinion ^^
In real life :
1) Song Hye Kyo with Lee Byung Hun
- Too old for her, not handsome, not sexy. Just famous
2) Song Hye Kyo with Rain/Bi
- Younger 1 year than her is not really a big problem but he is not handsome. I admit he is a good singer and dancer which make him looks sexy, cute. Still i doubt they are match to each other
3) Song Hye Kyo with Won Bin
- I think they are great and match. If both of them can make it then they are really a perfect to each other. Because both of them are handsome and pretty, sexy.
- Won Bin is also very cute, although he is a little bit shy type like Song Hye Kyo mentioned about him when "My Girl and I" pers conference

but he doesnt have the opportunity to be the leading role in Autumn Tale last time

that's why they dont get very near last time

Hope they meet in the movie or drama again