As most have said, I would agree that the terms (and the emotions relating to those terms) are very subjective. The cliche, "Beauty is in the eye of the beholder," comes to mind. However, from my own personal experience, I have two comments:
First, as a society we are constantly inundated with supposed beauty. Every time one turns around there is a commercial, magazine article, TV show, etc. depicting some beautiful person, vacation spot, product - what-have-you. With this barrage of beauty, sometimes the contrast of a little misery is needed. Sometimes we need to see the opposite side of things to keep our own lives in check, in perspective.
Secondly, I grew up in a small town in the Midwest. I left for college and ended up spending the next 10 years in the sunniest parts of California. I might have seen rain three days a year (and what "they" would call rain is really a light mist or drizzle that barely got anything wet, and still hardly a cloud in sight. Now that I have moved back to the Midwest, I cannot express how much I have missed the inclement weather. Now, thunderstorms and blizzards are my favorite kind of weather, and I can't wait to get out and photograph whatever it is that Mother Nature has to offer.
This second point may simply be an anecdote defining the first point; but it must be said, sunny weather doesn't do much for me any longer. I'd much rather have a miserable day now after so many days of sun. Helps me to appreciate all of it even more.
My weather story could be used to correlate to any of the other miserable things in life; and in photography specifically. I recall seeing an image in... well, it might have been National Geographic or Life... of an empty Operating Room with the remains of medical equipment and other debris following the frenzied attempt to save a man having a sudden heart attack. Quite a miserable image for most; but hopefully it is thought provoking enough for viewers to contrast to horrid thoughts of dying from a heart attack with actually living their life (at least, that's what it did for me).
That's why I think miserable images could be popular. Because it allows viewers to contrast that misery with the beauty of their own lives.
Maybe I have repeated what others have said, but this is the best way for me to explain why I think sometimes miserable images are better than beautiful images.