I have a hard time picking a favorite genre because, it is often changing. Right now I am on a science fiction kick. I will always have a soft spot for fantasy.
I tell people my favorite is Fantasy but if you look at my track record you'll see I spend a lot more time with Alt. History/Steampunk and SciFi or books that skirt the edge between Speculative Fiction and Fantasy. I like aliens, weird technology and I'm not good at making decisions so *shrug*. I think the distinct lack of Fantasy in my life has to do with the lack of REALLy good dragon books that I haven't already read.
Any non-fiction social sciences books (e.g., history, anthropology, etc.), mythology and folklore, fantasy (but I tend to be very picky. I'm partial to military fantasy), and horror/suspense (but I like only one author in this genre).
How do you guys feel about people reading only one specific genre?
I think they are missing out on a lot if they stick to one genre. I have favorite books from a wide range of genres. To me, it seems like each genre speaks to a different aspect of life.