Generally speaking, Williams/Bally/Midway pins have a certain "feel" to the way they play. It's hard to explain, but since most people grew up playing Williams pins (at least this generation of folks), it kinda became the industry standard. When you play a Gottlieb or a DE or Sega, it loses something. The closest I ever found personally was Hook. Data East pin, but really felt like a Willams play to me.
If you have a chance, play some different pins, Sterns, Segas, DE's, and then go back to one of your more well liked (NOT favorite) Williams machines, and I think you'll see what I'm trying to get at. Maybe someone else could explain it better.