I love watching Asian dramas as an alternative to American TV because I like my stories to have a beginning, a middle, and an end. I watch mainly Korean dramas because they have the best production values, and more importantly, they're most likely to resonate with me emotionally. I admit, I'm a huge romance fan, and I find that Korean dramas do love stories best (though I do wish they'd portray more of the passion aspect of love).
When grading the dramas I've watched, I'm unabashedly subjective. I don't really care about the objective quality of the drama; I only care about whether the story moved me personally--an outcome for which the rules are mostly fluid and sometimes surprising. In any case, I grade based entirely on my subjective impression of the plot, the characters, and of course, the love story. Especially the love story. If I love the character chemistry and the romance, I'll forgive a multitude of plot-related sins and give a high grade based on my sheer enjoyment of the drama. Conversely even if, viewed objectively, a drama is very high-concept and well-made, if it doesn't touch me emotionally, I won't grade it highly.