My parents took my sister and I the first year the MK was open and several times after that, sometimes bringing along my favorite cousin, so for that I'd say the '70s. I visited a few times with my family in the '80s, although my dad had passed away. Epcot was so much fun in its early years. One time we took my 90-year-old aunt and she had a fine time! So those are good memories as well.
There was a long break before I visited DW again in the late '90s, a few times with my family and another time with my boyfriend. Those were great visits as well, with most of the original attractions still at Epcot and the addition of MGM Studios. Once again, those memories are awesome. Most recently, my husband and I have been three times between 2007 and 2010. These visits were different from my previous ones in wonderful ways and also they brought back all those former precious memories.
So for me, ALL the decades of DW have been magical!