Good question!
Animal Kingdom has no nighttime show so we can skip that park.
Hollywood Studios offers
Fantasmic! in an amphitheater where the stage is separated from the audience by a moat of sorts. There is mist spraying up from the water and movie images are projected onto that mist (which is really cool!). The short storyline is that Mickey battles all of the Disney villains in a dream. The downside to this show is that it's a long walk to the very crowded theater. Plus, if you have a rented stroller it will be gone after the show and many feel it's too frightening for small kids. My kids have never been scared and this is my husband's favorite show. I personally could take it or leave it.
Epcot offers IllumiNations, set on the water surrounded by World Showcase. The main feature is a spinning globe with fireworks and pyrotechnics. There are images of all seven continents projected onto this globe, and a lovely lighting of all the landmarks around World Showcase (which is my favorite part). It's easy to get a good viewing spot for this show which is a big plus, but it's another one that I can pass up if need be.
And finally the crown jewel of nighttime shows (at least in my opinion) is Wishes in the Magic Kingdom. This is an absolutely-cannot-miss-it show for our family, and we usually watch more than once a trip. Narrarator Jimminy Cricket walks you through Disney dreams and wishes, with music from Disney movies ranging from Pinocchio to Aladdin. Cinderella's Castle is the backdrop, Tinkerbell flies, and beautiful fireworks light the sky. This one gives me chills every time, and I've been known to brush away a tear or two. (But I'm a Disneyphile so this is not surprising)
Whatever shows you see, you're sure to love them. Enjoy your trip!