"The Marvel characters are not just about how high they jump or how fast they fly, they're about their character flaws," Feige said. "They're about their inner demons. They're about the struggles that they go through between being a man and being a hero."
Downey, who has battled his fair share of inner demons, worked hard to get the role, getting in shape and even growing a goatee like the one Stark sports in the comic books.
"In every casting announcement we've done, people in their mind's eye have their own view of it and let us know about it. We're used to it," Feige said. "The point is, we looked at everybody, and we found the best person for the role. It's as confident a casting move as we've ever done. The proof will be in the pudding, but he is Tony Stark."
looks like RDJ actually knows the character and wanted the role.
I'm really glad someone of Robert's calibre got this role, look at it this way, if a big mega star like Tom Cruise got the part, a huge chunk of the money would've gone to him and it would've been "Tom Cruise" movie not and Iron Man movie, and casting an unknown for the part wouldn't have worked because IM's not as well known as Superman or Spider-man.
RDJ is a solid Oscar nominated actor, who looks like Stark, wanted the role and even battled inner demons, like Stark