I write in speculative fiction. Scifi, superhero, steampunk, (urban) fantasy, paranormal - it's pretty much always one of those, with elements of several other genres thrown in (I don't stick to pure genres either). I play with horror, mystery, suspense, romance, adventure, war... and probably some others, but always under a speculative umbrella.
How long since have I gone writing outside of that? Hmm. Maybe a short story? It's pretty unusual for me to step outside speculative fiction into straight/realistic fiction. I keep thinking that I should try my hand at one of the super-popular genres for the money, like erotica or romance, but they just don't speak to me on their own so it hasn't happened yet.
I also tend to write from a strong character standpoint. The rest is the kind of atmosphere and scenery that interests me and lends me fun tools with which I can beat said characters about the head.
I think I saw Rosemary's Baby once upon a time, but I barely remember it. Why are they remaking it? Because remaking stuff is really fashionable right now and it's easier than creating something new. Or maybe it's because studios know that remakes will get them a certain amount of returns because of the built-in fanbase and it's easy to get projects funded. I'm not really sure, but there do seem to be a lot of remakes around lately.