I like your method so I think I'll copy it.
Magic Kingdom:
-Overrated--Dumbo (I get it, but it spins...that's it woooo)
-Underrated--Carousel of Progress (always try to convince other guests to ride it)
Epcot:
-Overrated--Soarin' (doesn't come close to real flying, boring)
-Underrated--JII w/ Figment (not the original, but still underrated)
Hollywood Studios:
-Overrated--Toy Story Mania (a video game, with a huge line)
-Underrated--MuppetVision 3D (just hilarious for all ages!)
Animal Kingdom:
-Overrated--Kali River Rapids (will not go on again if I have to wait for it, horrible queue)
-Underrated--Dinosaur (great thrilling ride)
also, the park as a whole is largely underrated (great themeing, just needs a little growth to top it off)