I just think it was a blanket statement. I find it difficult to think that someone knows whether or not "most" fans were disappointed with the last two. Near as I remember, they did fine at the box office. It has just been my experience that film critics are generally the least qualified people on Earth to criticize films.
Sure, it's a blanket statement, but so is "Most people didn't like Battlefield Earth." It's pretty common knowledge that MOST fans think the two best SW movies are SW and Empire, and then Jedi, and then the other two. Box office is tricky--people pay to see movies based on hype, but that doesn't mean they liked them. The first two prequels are basically kids movies--Clones is the first SW movie to not be #1 at the box office for its year. That's a striking fact, and it sure says something about what people thought about Phantom Menace.