The blockbuster, which also features Robert Downey, Jr., Samuel L. Jackson, Jeremy Renner, Chris Evans and Scarlett Johansson, has already grossed $180 million (£112.5 million) worldwide and it will be released in the U.S. on Friday (04May12).
The bumper figures have prompted Marvel movie bosses to sign Ruffalo up for a series of sequels and other projects, which is likely to include a new solo outing as the green monster - and the actor admits signing on the dotted line was an easy decision to make.
He tells Collider.com, "I was so impressed and blown away by how much (director Joss Whedon) packs into this movie and how exciting it is and what a great ride it is, and how it just works on every level."
Actors Eric Bana and Edward Norton have previously portrayed The Hulk in 2003's Hulk and 2008's The Incredible Hulk, respectively.
Jackson has a similar deal in place - the Pulp Fiction star is committed to making a total of nine films as Marvel army hero Nick Fury.