In June/July 1999 (first visit since early 70's), I got to ride Rock n Roller Coaster in soft opening. I did not even know it existed, as it was not in the Birnbaum guide book AAA gave me. I had no idea what the launch system was, or even knew such a thing existed. As a fan of rock music, I was loving the pre-show. Because the ride was not advertised, very few people were in line. I did not see a car launch in the alley prior to boarding! Again for emphasis, I had no idea what was coming! Shockingly good. (I still get a kick out of watching the reaction of first timers in the alley)
After that trip, I was well versed in WDW prior to any visit. I know information, but I refrain from ride videos. Others:
I agree with others above. When Lumiere lit his candle in Philharmagic, I was hooked.
I got to ride Everest after it first opened. When the show was full on, people literally applauded and cheered afterwards. It was awesome when in all its glory.
I was on my way to the Tower in 1999 when we got diverted by a CM to RnR. when I finally rode it, yea, I was impressed.