I think f/m is overlooked more than it is not liked.
However, I can say that, of the f/m stuff that is out there, a lot of it isn't that good. Of course, that is partially based on my personal taste.
I would usually prefer f/m, but I often catch myself going after f/f and m/f because (1) I also think that stuff is great, and (2) as much as I hate to admit it, female 'lees tend to have much better reactions to being tickled than do male 'lees--generally speaking, of course. I won't say most do this, but it seems that a lot of guys grunt, grimace, and try to hold in laughter when tickled. Also, a lot of f/m vid producers get guys who really aren't that ticklish, and what you see in the vid is a fem tickler doing an awesome tickle job on a guy that really isn't ticklish.
This seems to be changing, though...much to my delight.