Your examples easily proved your points, even if not all of them bothered me. I guess they are adding those kinds of relationships problems because of the "heroes are humans too, ya know?" theme.
You're right, the love stories in the recent Marvel films are rather uncomplicated, natural and don't get in the way. They play even less a role in The Avengers, thank God. I am even wondering if there'll be a super hero film without any love interest. Did Ghost Rider have one? I don't remember.