Absolutely fantasy, and I love what Sims 4 is doing with it, taking it slow and giving them proper depth.
Mind you, fantasy play needs the stuff the realism does too to work. So the division is more on the part of the realism-only players, they don't want any part of fantasy, although I feel the fantasy-players use all the content, including the parts realism-players like as well. I like the quote @EmperorDitto made above, that's exactly it. For fantasy to be really awesome, it has to feel realistic.