I don't know about folks who used to like the Star Wars prequels but now don't (I always disliked them personally), but it makes some sense that Iron Man may not hold up over time. That happens with lots of things. It was fresh and innovative when it came out. Now, we've seen his character multiple times and lots of sequels and other movies in that universe that have actually improved on what Iron Man 1 did. Things don't always stay fresh. Some people like Wofford were maligning Cap and Thor, calling them average, but a big part of that was probably expectations, which only went up after Iron Man. I bet if they came out before Iron Man people would have loved them much more.