First visit, 1961 or 62.
Sure, there's the nostalgic haze of childhood interfering with my judgment, but despite that, I would say that DL was better in the sixties in two ways:
1) Walt was driving the place. Look at the cascade of E-ticket wonders debuting practically every year between 1959 and 1969, most of them still there and most of them acknowledged classics that still pull in the crowds. It's just an objective fact that there's never been anything like it for sheer creative outpouring of theme-park genius and energy.
2) People were more civil. This is a cultural thing that Disney has no control over, of course. You dressed up (a little) to go to DL. You waited patiently in line. You said "excuse me" and "pardon me." Your kids were safe running around by themselves, and you didn't give it a second thought.