When I took my first trip to IOA during Christmas holidays back in 1999/2000 I saw a nearly 6 hour line for Spiderman. And no, I did not get in line!
It was quite funny, while half the people in the park were waiting to ride Superman I was doing countless laps on Dueling Dragons which was a walkon.....I just wish I new about that stupid shortcut!
The longest I have actually waiting inline though would be either for Hulk@IOA or Vortex@PCW (when it first opened). I forget exactly how long I waited for hulk but it was about 2 hours. I waited for about the same amount for Vortex because I was waiting for front seat during the first weekend it opened.