Yeah, late 80s to early 90s. EPCOT Center was fleshed out, MGM Studios was fresh, interesting and showed promise. Magic Kingdom was what it always was. The resorts and crowds weren't over the top and you could plan trips during periods that truly were ghost towns.
Too early into the 80s and you don't have MGM Studios, and EPCOT Center didn't have a lot of attractions it would see later. Too much into the 90s and you get into the upcoming, in my opinion, downfall. EPCOT Center becomes Epcot, or worse yet, Epcot __. Cool, original attractions start to disappear, such as World of Motion, Horizons, Wonders of Life, Journey Into Imagination, yada yada yada. Then there's the whole Era of the Wand(TM), the paving over of the reflecting pond and raising of the sail. Characters begin their invasion (e.g. The Three Caballeros). Hollywood Studios is much ado about nothing and sinking fast... BAH goes up. Though ToT was a killer addition.
No, mid-80s to mid-90s was the sweet spot, IMO. Unless you go back to '71 for the opening of MK. A bit barren perhaps, but cool in its own right... Just as '81 was for EPCOT Center.