I think crime and horror are probably the two most popular genres in fiction. There can be crossover and within each genre there is a wide range of sub-categories. But does this mean you should just write to these two genres, say, because you know there is a proven market for them? Absolutely not!
You have got to believe in what you write. You have got to love what you write (at least most of the time! I appreciate when you've been through the sixth rewrite, you may feel a tad tired about the whole thing! We all do!).
You have got to love your characters, and love those you love to hate. I also believe that if you don't write what is your "driving fictional instinct", what you do come out with will be just a poor imitation of the markets you are trying go get into and that will show. Whereas if you love what you write, that will also show. It is where your writing voice will come through loud and clear. Good luck!