Cmon. What basis at all did you have to think Favreau would make a good, serious Iron Man movie? Zathura, (a Jumaji remake) and a funny Christmas comedy?
Why don't you think that Marvel will land a B or C list director? Kenneth Branagh is a well respected director and Joe Johnson has done quality work. Joss Wheadon was a respected hiring based on his past work. Even Louis Leterrier wasn't too bad for a Hulk movie. All of these directors were more well known directors than Favreau was when he took on Iron Man. You have nothing to base your hunch on given these hirings and that of the actors they brought to their films.
As for Nolan, he wasn't a big name at all. He was a rising star because of the two movies you listed, but not an A-list director. Iron Man put Favreau in the position to do bigger work in the same way Batman has for Nolan. I don't see why this can't replicated for Iron Man 3.