As a husband and father of two young kids, MK, is my favorite. Walking down Main Street with my kids reminds me of doing the same with my parents when I was their ages. There is nothing better than going with your child on his first ride on Thunder Mountain.
As an adult and a husband, EPCOT is a not to distant second, because walking around World Showcase in the evening, with the torches lit, after enjoying a great dinner and partaking in some adult bevages around WS is a lot of fun as well, especially if you're staying at an EPCOT resort and can just walk in to the park from the international gateway. Future world, while nice, doesn't hold a candle to MK, IMO though.