I personally think Figment has, simply because of the fact that it went from what the Youtube videos show to be a pretty good dark ride to... well, what it is now. In terms of actual physical aging, I'd agree that Space Mountain has aged the worst (and really deserves to have its track replaced, piece by piece) but in terms of aging as in how old it feels, Figment's really starting to show its age. Song's still really catchy, but the ride itself has definitely deteriorated in terms of show quality. At least Space Mountain is still extremely enjoyable, despite the occasional headache from its rickety track, and its queue is pretty nice.
Don't get why PotC is on this poll, it's still a decent dark ride with decent show quality despite the updates being considered negative. And I've never been on Everest (though I do plan to someday) so I can't speak on that one, but if it's mainly about the Yeti, I'd say that it really hasn't aged horribly for a ride that probably has some structural damage from the most elaborate show element in... well, probably any roller coaster.
