Mark Ruffalo has played Bruce Banner/The Hulk in five films, but he's never played the character in a solo movie. But that's not for lack of ideas - in fact, Ruffalo has his own concept for what could make a perfect Hulk movie with his version of the character.
“There’s an idea that I think could be really interesting,” Ruffalo told Variety. “We’ve never really followed him into his life. He’s always kind of off on the side. He’s like the Rosencrantz and Guildenstern of the Avengers. It’d be interesting to fill in all the blanks about what happened to him in between all these movies.”
Hulk's last solo outing was 2009's Paramount Pictures-produced The Incredible Hulk, which starred Ed Norton in the title role, however Ruffalo replaced Norton for Avengers. Reported film rights issues that would allow Paramount some input over a solo Hulk film have left Hulk relegated to the role of supporting character in Marvel's ensemble films - but he's become a fan-favorite character nonetheless.
As for whether he'll appear as Hulk again, Ruffalo re-confirmed to Variety that he's been in talks to appear in Disney+'s She-Hulk show, but nothing has been confirmed.