I'd have to say my best was Oct 1999. It was just a long-long weekend, but is was really magical.
We went with a group, and we had a really good travel agent who booked us during the premier of Tapestry of Nations. She also managed to get us into Jamaica at CBR, which IMO is really the best place to be at that resort. The crowds were light, too.
At Epcot during the premier running of ToN, I can't remember ever being in such awe in my whole life (except maybe my first 14 July in Paris under the tour Eiffel, or when I first saw St. Michel, or seeing my bride walk down the isle, but even those times were different). DD6 and I got filmed playing with the big, tall stick people in the parade. They said it was for the advertising promotion videos that would be before Wonderful World and on the Disney channel and other venues to promote the millenium celebration, but if we made the final cut, we never saw it or heard about it from anyone. It was fun hamming it up for the cameras, though.
My DDs were 6 and 2. DD6 had been to DLP when she was 3. When I was planning which parks to visit when and getting ADRs (PSs back then) I asked DD6 what she remembered most and liked best about DLP. Out of all the things we did there, she said the most exciting thing she remembered was that Goofy came over and shook her hand while we were eating in Pizza Planet:lol:. So I basically planned the weekend around character meals, and what a good idea that turned out to be!
DD6 bought a crown at PoC the first day, and wore it everywhere the whole trip. DD2 was just starting to talk, and didn't shut up the whole weekend - look at this, look at that over there, can we go on such-and-such please - and she talked to the characters a mile a minute. They were both really cute and charming, and the characters spent a lot of time with us.
One night we got babysitting and went out to DtD. Ate at Bongos when it still had a floor show and wasn't yet a big latin disco meat market. There was a Desi Arnez impersonator there who was really, really good. Saw Christina Aguilera at PI in her first large-scale public appearance. You could tell she was a bit nervous (she said she was nervous, in fact), but her performance was top-notch (this was before she was all racy and such).
The babysitter turned out to be a really good one. Took them to the playground, dinner at the food court (they chose burger buckets) and then to the beach to play in the sand, then back to the room for games and Disney videos. They were asleep when we got back (we stayed for the then-nightly new year's eve stage show and fireworks at midnight), but by their report the next morning, they had a better time than we did!
Altogether a magical trip for all!