I do think it's interesting that a lot of Marvel Studios fans very much dislike the cinematic universe approach when another studio tries to do it with another concept, and I think the most common explanation is that with the others they were too rushed in trying to set it up. To me even if they are more rushed, too rushed, that shouldn't be the difference between loving one and strongly disliking another.
I do think a big part of the success of the films is from the casting of RDJ as Iron Man and Evans as Captain America and frankly that a lot of general viewers did have low expectations for those characters and then grew attached to them.