Re: Who deserves the most credit for MCU: Phase One success?
Feige, mostly. Favreau, second.
It was Favs who took the bold step to cast RDJ as a superhero, and to take a new non-Burton/Nolanesque approach to the genre. More importantly, he's the one who came up with the idea of using SLJ in the Nick Fury cameo at the end of the movie, and urging Kevin Feige to actually develop a shared film universe.
But Feige has been the one who's responsible for the logistics of bringing all this together, and he's done an outstanding job, with an eye towards genuine respect for the source material and fandom.
THE COTTON AVENGERS
...They move like slick cotton on oil.