Dan, I wish I had a dollar for everytime I've heard the "just another amusement park" line. It's usually from someone who's never been there.
My best argument is that if you want to go someplace and eat greasy food and then go on rides so you can toss it, then you go to an "amusement park." If you want to go someplace and be entertained, educated, relax, and still have some options for thrills, you go to WDW!