I was thinking about the Iron Man movie compared to the Dark Knight, and the reasoning that TDK beats IM in the sense that the Joker is a significantly more noteworthy villain than Obadiah Stane/Iron Monger. Now granted a movie interpretation of the character could be a change for the better from the comics, but if you ask me, the Mandarin isn't that much better of an option for a memorable villain. And a superhero is defined by his villains, or something like that. And we have a really strong start for Tony Stark with Robert Downey Jr.
I got to thinking about the rest of Iron Man's rogues gallery, and the best option I could think of for a show-stealer was Dr. Doom. (Yeah there's the “iconic” Richards/Doom rivalry, just stick with me here on this.) They could do a light re-boot of the character to get him away from the Doom in the FF movies, and get him ready to be a possible major player for future Avengers movies.
But that also brought another thing to mind. When Marvel sold off the movie rights to properties like Spider-Man, the X-Men, and the Fantastic Four, is it known what exactly was packaged with them? As far as supporting characters and the villains they could use, like for the Fantastic Four, would the deal just have been to use Reed, Sue, Johnny and Ben, and first come first serve with anyone else? Would Doom have been included in that deal? I read somewhere that there are no current plans for FF 3 which might render it a moot point anyway, but how did those rights selling deals work?