"He has my vote for sure," Favreau told Variety when promoting star-studded Netflix cooking vehicle The Chef Show.
"I think he was able to discover and explore dimensions of the character over the course of many, many films, which is a bit of its own category. But I have to say that if you look at, especially how it began and how it ended in his performances between the first one and Endgame, there was a really thoughtful arc to the character, both in his performance and how all the filmmakers contributed to that character."
Favreau set the course for the armored superhero and the shared Marvel Cinematic Universe when directing its premiere feature, Iron Man, steering Downey a second time in Iron Man 2. Favreau then served as executive producer on the Shane Black-directed Iron Man 3 and earned that same credit on all four Avengers films, headlined by Downey and an assemblage of stars.
"I'm glad I got to be a part of it and be there for those meaningful scenes as an actor, but also to be there as a friend, and to watch him explore things deeply through a character [when] you don't normally have that opportunity," said Favreau, who stars as Stark's right-hand man Happy Hogan, a character set to reappear in July's Spider-Man: Far From Home.
"And he took full advantage of it."
Marvel guest stars on the series include Downey and co-star Gwyneth Paltrow, Spider-Man star Tom Holland, Marvel Studios chief Kevin Feige, and directors Anthony and Joe Russo.
"The Marvel crowd, that's a family, For over a decade," Favreau said. "So, when it's Robert and I, we have this whole shared experience of what we've been through. I don't think I've ever seen him cook a lot of stuff."
Downey also has the support of his Avengers directors, who earlier told the Washington Post the longtime Iron Man star's "cumulative body of work from these movies is staggering."
"If you look at the work over just even the last four [Marvel] films he's done, it's phenomenal... He deserves an Oscar perhaps more than anyone in the last 40 years because of the way that he has motivated popular culture," Joe Russo said.
And because of Downey's "heartbreaking" final turn as the armored Avenger, "He has the world in tears right now."