The director hopes to improve as he brings Marvel Comics' greatest superhero team together in the sequel, reported Entertainment Weekly.
"When I think of a great film, I think of something that's either structured so perfectly like The Matrix or made so lovingly like The Godfather Part II. There was haphazardness in the way it comes together - not just the people, but the scenes. I don't think you'd look at it and go, 'This is a model of perfect structure.' You'd go, 'This is working.'," Whedon said.
"I like it. I'm proud of it and I like its imperfections. The thing I cared most about-making a summer movie like the ones from my childhood-is the thing that I pulled off," he said.
The film stars Chris Evans, Chris Hemsworth, Cobie Smulders, Gwyneth Paltrow, Jeremy Renner, Mark Ruffalo, Robert Downey Jr, Samuel L Jackson, Scarlett Johansson.
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In 'Avengers' sequel 'Age of Ultron', superheroes Iron Man, Thor, Captain America and The Hulk will take on the titular robotic villain. The writer-director said he already knew how to make the film a better movie.
'The Avengers: Age of Ultron' is due out in 2015.