Both fantasy and romance are their own distinctly different genres. Whether the fantasy is front and center and the romance is secondary, or whether the romance is primary and the fantasy is secondary depends on how the creator wants it to be. Neither can be considered to be a subset of the other, even if romance gets the top billing most of the time. The same goes for any pairing of genres. Romance/comedy, comedy/drama, etc.
I personally don't recall more romance movies with fantasy being secondary like Stardust or Princess Bride than I do movies that were fantasy first and romance second like Lord of the Rings, D&D, Narnia. To my recollection most of the time the fantasy movie just happens to have a few characters that are/become romantically involved, but the fantasy portion is still the primary focus of the movie or book. Where are you getting your numbers from?