Call me a traditionalist, but I prefer boy x girl. But no romance works too, I've seen romance written poorly (1 dimensional, just to move the plot) where the MC would be better off focusing on cultivating/transcending and working on the plot of the story.
I am about to pull my rainbow flag out just for lulz but seriously, I don't really care if the scenes are good and well prepared, no hogwash sudden love at first sight shit that is most definitely lust. The rollercoaster effect can be used once in a while, but please do some buildups and compatability checks.
MxF are likely being first primarily because Novel Updates also started with simple romance. FxF are the second highest while MxM isn't rated much due the readers that prefer the story(Mainly guys or girls who prefer that). However, NU slowly began to dump more and more MxM stories to which ScribbleHub wouldn't escape its own fate of having more MxM in the near future so by sometime passes, there will be more MxM than MxF or FxF. Only time will tell.
I used to not care much, besides not having any interest in BL main couples (not that I read a lot of dedicated romance stuff), at least with books (not that there was a lot of BL or GL in mainstream books).
With manga (and anime), I've always sort of had a thing for GB in general (with the occasional GB-GL). More recently, I've really taken a liking to GL manga (GB or not). On the off-brand side of manga and anime, GL with extra equipment has been fascinating for a long time.
Now, since I came to SH, I've sort of shifted to mostly GL, with only a few stories with MxF pairings I still read.
Recently, I have a hard time even getting interested in stories with male protagonists, while GL is almost an auto-include on my ever-growing list of stuff to read one day.
Still very much no interest in BL as main couples, though I don't mind them for supporting cast (gotta find a place for all the males anyway).