Hi Jennifer,
There are 3 main fireworks displays:
Magic Kingdom has "Wishes Nighttime Spectacular" See this link:
Wishes . This is best seen from a vantage point in front of the castle so you can watch Tinkerbell fly from the top of the Castle over to Tomorrowland.
Epcot has "IllumiNations: Reflections of Earth" See this link:
IllumiNations . There are many prime viewing spots located around the lagoon in World Showcase, stake claim to your spot about an hour before the show.
Disney's Hollywood Studios has: Fantasmic! See this link:
Fantasmic! Arrive at least an hour early to get a seat.
To choose a favorite among these would be like asking me to choose a favorite star in the sky. Honestly. They are all absolutely breath-taking and stunning. Each one has a different theme, and they all bring tears to my eyes (literally). If you can, I recommend you find a way to see all of them. We plan our itinerary around the fireworks, since they are not all offered on every night. Call 407-W DISNEY (407-934-7639) with your travel dates handy and ask them when the various fireworks are offered during your stay.
Hope this helps and have a magical vacation,
Kaylene