Re: Who deserves the most credit for MCU: Phase One success?
From what I understand, I have to go with Feige.
Obviously if you take Downey or Favreau out of the picture, things change completely. Same thing with a mediocre Avengers without Whedon's involvement. But all of those things were made possible because Marvel, and therefore Feige, made the deliberate choice to hire real directors such as Favreau and Whedon (and Johnston and Branagh), and genuinely great actors like Downey and Ruffalo, and have them written by people who actually care about and are faithful to who, for example, Steve Rogers is. Not to mention the devotion to the source material in general.
None of that was a safe bet, we could easily be living in a world where Ryan Reynolds is Tony Stark and Michael Bay is directing The Avengers based on a David Goyer script. Feige got that ball rolling.