The sequel "Avengers: Age Of Ultron" will also be directed by Joss Whedon. Marvel's creative genius has set a very high standard for his follow-up movie: "The Godfather 2" which is hailed as "The Greatest Sequel of All Time."

"The Godfather 2" was all about character building-when we get to see how Don Vito became who he was, and the continued development of Michael Corleone's character as he becomes immersed in the dark side of his family's 'business.'

Whedon praises the film and its approach on continuity. It's a sequel but you don't feel like you need to watch the first film. It is also acknowledged as a better film than the original.

Whedon talked to Total Film:

"The model I'm always trying to build from is 'The Godfather: Part II,' where a ton has happened in between and it's a very different movie, but you don't need any information... You're in the vernacular of the first movie and you're ready to just pick up in this new place.

It's got a sci-fi element to it that's stronger than the other film. And it's a little bit darker. Getting the team together was so rousing, but keeping the team together is a completely different problem."

With regards to the sci-fi film, the theme of developing human-like artificial intelligence plays a heavy role in the film. The ideas of a dystopian future where machines take over humanity are familiar topics. But in the Avengers, Tony Stark is in the middle of it all. In his ambition to stretch the limits of controlling artificial intelligence, his creations overpower him and his allies.

It could also be an interesting twist if the Hulk would be the one to stop Ultron. We have seen the concept art of the Hulk against the Hulkbuster armor, which many suspect was controlled by Ultron in some way.

These are interesting possibilities, but we need to see how Whedon will execute on May 1, 2015.