I just tell them, "Yup! Some people like to go to the same beach house (lake house, cabin, ski resort, etc, etc) every year- we like to go 'home' to WDW."
Usually I find the ones who act so snooty about WDW either have never been because they think it's "just an amusement park", or went once and hated it because they didn't do any planning.
I just smile and think to myself, "One less family in front of me in line for Space Mountain!!" I don't even try to convince people that WDW is wonderful- if they don't "get it", I'm not going to let it bother me.
BINGO! This is something I have yet to figure out! The same people that ask me this are the same people that go (quad-riding 3-4 times/yr, Hawaii and Mexico every year!)
I have a friend, who has never been there, by the way! She said to me one day, not in a mean way, like some do, "Don't you get tired of going there?" I started thinking-should I just blame it on my son, but thought, his Dad and I like it just as much, if not more! So, I replied, "Well, no!" "There is so much to do there and we love it!"
The funny thing is this same friend went to Mexico for spring break and me and another friend found out she bought a timeshare there and she didn't tell us! I said to her, "You must really like Mexico!"
She replied, "We love Mexico! We have been there 8 times!"
I couldn't help myself and responded, "Reeeally! Don't you get tired of going there?"

Then I chuckled and made my point as to her liking Mexico and us liking Disney.

She never thought of it that way!