Oh, such a good and yet tricky question. If I could only read one type of story I would have to say something with a bit of angst that concluded with a happy ending, hot smex a bonus.
That said I do enjoy a bit of dark and twisted from time to time--depending on what is dark and what is twisted, definitely first time as a plot device, I am not at all opposed to PWP *vbg*. I think in the hands of the right author I can at least try almost anything.