Nostalgia has a big part of it, but I also think that it may be what replaced it and variety are just as important as how much it was loved. I think Universal in general has a hard time creating nostalgia, just because they replace and change things so often.
Was Twister good, no not really unless you were a fan of Canadian Tuxedos but I would rather do it than Fallon and same goes for Fast and Furious and Disaster, just because they were different and well better, but I don't think nostalgic is an accurate word.
Yes I am nostalgic for Jaws, it was amazing for multiple reasons but most of all the skippers. It was a one of a kind ride at all of Universal. Diagon is an amazing area and a good ride, but man I miss Amity and Jaws.
Heck I even feel a little nostalgic for Old Hulk vs New Hulk
The entire Epcot conversation is very different as literally every ride with the possible exception of Test Track was better than the one that replaced it. Horizons, Figment, Old Spaceship, Maelstrom (only because of the Arindale problem).
I think HHN is a different beast too, the older years of HHN were very different than anything since Walking Dead showed up. The event had a completely different feel so I think that put you in a different mindset for the houses.