Ohh, this is fun- I couldn't limit each park to one ride, so here are my favorites:
MK - #1-Big Thunder Mountain, #2-Haunted Mansion, #3-Peter Pan's Flight (Come on people, am I the only one?)
EPCOT - #1-Horizons (RIP), #2-Maelstrom, #3-Test Track
Studios - #1-Muppet Vision 3D, #2-...