My first few trips occurred before EPCOT opened (yes, it used to be in all caps). So for me, it's an easy choic, even though I love the other parks, too. Magic Kingdom is the quintessential Disney.
Ok, I'm going to get shot down but hey, I don't think any one park is a must do in itself or is great by itself. I think what makes WDW so great is the sum of it's pieces in all the parks to make one great experience. If I had to pick one, I'd have to pass. I have to experience all four.
Absolutely.
MK is the ultimate Disney experience.
Epcot would be a fantastic place for the wife and I to just kind of wander around, have a great meal, a couple margaritas, and watch some of the various entertainment options.