Not sure what all I can add that hasn't already been said. What I would like to say is that, as odd as I might find them, others have a right to their own fetishes, and realize that they may find my own odd as well, and that none are necessarily "better" or "worse" to have or fantasize about. As with everything else in life, it's completely subjective. There may be some things that fall more into morality and what is decided as right or wrong within society, but I still do not believe that makes anyone necessarily bad.
As for myself, femdom has brought a ton of different ideas to mind, a lot of which crossover into other kinds off kinks or sets of kinks, and it's apparent not everyone agrees with absolutely all of them. People have different tastes.
The idea of a futa is not something I was initially interested in; I might say I had a sort of mental block about it. It's something that seems many people like for a lot of varying reasons, but for myself, I think it's the fact that it would be near the ultimate submission to a woman. And yet, like others have said, I'm not so sure I'd be as fond in real life, even if not too terribly different than a strap on.
Incest is a bit more 50/50 for me. It really depends on the characters and plot and just generally what's happening, so it's very situational. Would prefer to have it be an older sister/younger brother type of scenario, as anything involving parents and a child would be too close to child abuse for me.
There is definitely a difference between fantasy and reality, and perhaps a sort of scale going from one to another - on one end you might only want to fantasize about it and nothing more, while on the other it would be something you'd like to try very much. Perhaps somewhere in between or branching off of it would be the option to do neither, and that's ok, too.
Going off of that, I don't know about anyone else, but I don't like to think of myself so much in these fantasies, especially with stuff like incest involved. I would never want to do this with any of my own family members, and I can't imagine too many others who would, as you know them as more than just sex objects. In a fantasy, you're not caught up in every day life or with people you know that would make things just overly awkward. It is a very different mindset.