Horizons, followed very closely by Journey Into Imagination.
ed: World of Motion would be very close on the list, too. I suppose my quote below says it best. EPCOT was in so many ways superior to Epcot. I know I'll get reamed for being a purist, but it's actually not true. I prefer the Ellen's Energy Adventure to the old UoE, Circle of Life to Symbiosis, and Reflections of Earth to the other Illuminations shows, so I'm not completely against change...just change that doesn't seem to promote the original idea behind the EPCOT that opened in 1982.