I have watched both the original ( the Chinese version "Go Princess Go") and the Korean remake ( Mr. Queen). And I have to admit, I think I like the Korean one a little bit better. Don't get me wrong, the Chinese version is just as good. But I found the Korean remake to be slightly more entertaining.
The Storyline- similar to the Chinese version, the FL ( a male at the time) is a selfish playboy who while running from someone, ends up falling into a pool which sends his spirit back into the body of a Queen (to be) of the Joseon Dynasty. And just like the Chinese version, he tries everything possible to get back to his time period. which brings about some very funny situations.
Prior to his soul entering the Queen's body, the Queen (So Yong) was disliked by everyone including the King. But the spirit in So yong's body, despite being rude and stand-off-ish, is somewhat kind and caring. This causes people around to begin to see the Queen in a new light. There is some love rivalry, but it doesn't last long enough to bother you and it doesn't get too heavy on the politics either. it is the perfect mix of mystery, comedy and romance.

The cast-I loved the cast in the original, they did a good job. But the Korean version's cast was just Awesome!
I had seen Shin hye sun in other dramas but wasn't as drawn to her in other dramas as I am am in this one. her ability to show a different range of emotions really made this drama light and fun to watch. Her character is the main comic relief in the drama.
I had also seen Kim jung hyun in other dramas but became a fan of his after seeing him in Crash Landing on you. The rest of the cast also did an amazing job.

I've seen some complaints about the ending but I think it was an ok ending. Everyone was happy in the end.