Since entry hazards were introduced Starmie has been hands down the best Rapid Spinner in OU. That niche isn't going without some massive upheaval, I doubt another Pokemon with such amazing coverage that makes it impossible to spinblock is going to come along and if it does it will have to be pretty amazing to outclass something as fast and powerful as Starmie.
Gengar is a cool guy and all, but it lacks any sort of solid niche other than being a Ghost type. It's so far been lucky enough to get something cool every gen, like being the fastest sleeper in Gen 1, then being able to kill Blissey with Focus Punch in Gen 3, getting usable STAB in Gen 4 and then Sub Disable this Gen. I think its luck has got to be wearing thin, and there's only so many new toys they can keep giving it.
>>12965916No it isn't, there are unlikely to be more than about 20 Fairy types, and so few of those will have the stats and moves to make it in OU that they will be nowhere near game-defining.