I wonder if I'm the only one who has MK at #4 on their list. If I had a short trip with only time for three parks, it's possible that MK would be the one that I'd skip.
The thing that might save it in that scenario is that two of the Dapper Dans are good friends and I would hate to travel all the way to WDW and not visit them. (In that case, I'd probably skip the Studios.)
Epcot is hands down, far and away my favorite, and AK is an easy second.