It's safe to say that the success of Korean movies used to be mainly dependant on star power. Regardless of how original a plot line was, how well the production was made, and how cleverly written a script was, none of it mattered as much as how big the names of the stars involved were.
However, that's slowly but surely changing. Now, just because you have some of the most well-known faces in the industry does not mean a movie project is guaranteed success. Directors and producers are starting to realize the importance of meeting the needs and desires of their movie-goers.