The last big Hulk video game came out in 2008, right around the similarly-forgotten "Incredible Hulk" movie, which starred Edward Norton as the titular emerald giant.
But we've yet to see Mark Ruffalo's Hulk, as seen in the "Avengers" movies, in a proper video game. It could delve deeper into one of the best dichotomies in the recent films of the Marvel Cinematic Universe: The life of the nerdy physicist Dr. Bruce Banner, and his monstrous alter-ego that's released when he's intensely excited or angry: The Incredible Hulk.
Imagine a "Grand Theft Auto" scenario: You're a character in a big open world teeming with people you can interact with, as Dr. Bruce Banner. But if you build up too much anger or energy, you transform into The Hulk, which has consequences both good and bad: It makes you incredibly strong, but it also makes you a big target and easily attracts enemies to you. Perhaps utilizing the two different characters at different times could be used to solve puzzles, or change the outcome of your game.