Check your stay dates to see what the park hours are. The
Disney web site has a calendar with that information.
Disney's Animal Kingdom is typically a one day park and it closes the earliest. A Bugs life is fun and I can just check out the Tree of Life for a long time.
Disney's Hollywood Studios you can see in a day if you rush and it is a long day. There are some rides like Rock-n-Roller Coaster and Tower of Terror that my kids enjoy multiple trips on. My favorite shows are the Muppet Vision 3D, Lights, Motors, Action stunt Show and Fantasmic.
Epcot you can see in a day to a day and a half depending on how much time you spend in the world showcase. Adults like the shops but the kids are looking for action. There are a couple of rides tucked away in the World Showcase pavilions. Maelstrom in the Norway pavilion is good. The kids like Mission: Space and Sorin' is pretty cool.
We always ride Test Track and close the night out with Illuminations.
The Magic Kingdom takes two full days if the crowds are small. There is just so much to see and do. The Kids enjoy the mountains, Space, Big Thunder and Splash. Mama and I enjoy going over to Tom Sawyers Island. There is a picnic table on top of the island in the shade. We can just sit there and chat while the kids plummet themselves silly (mine are teenagers and can run around together tied to their cell phone leashes). My favorite coaster is Goofy's Barnstormer in Toon Town. It is a simple little kiddie coaster but its a hoot. There are too many good rides and shows to even start a list. We just start in tomorrow-land and work our way around.
The water parks can be a day in themselves. Downtown Disney and Pleasure Island can be a good escape from the parks one night too.
Ultimately how much time you spend in each park depends on how much you want to see and do, how well you plan out things like FastPass and dining and how crowded the parks are.
For those staying on Disney property, take advantage of the Extra Magic hours that the parks are open exclusivly for Disney resort guests.
Enjoy and remember, you are on vacation. You have no place that you have to be. I hope that helps.