Since his introduction in the early 1960s, The Hulk has been pop culture's most prominent Dr. Jekyll and Mr. Hyde dynamic. In one form, you have the renowned scientist, Dr. Bruce Banner, and when he transforms, he becomes the nearly-mindless rage monster known as The Hulk. Regarding the latter where the Marvel Cinematic Universe is concerned, it's difficult to make him feel like a compelling character given his animalistic state, but according to Mark Ruffalo, Thor: Ragnarok will help flesh out the Green Goliath, and it all has to do with his new surroundings.
He's much more of a character than the green rage machine you've seen in the Avengers movies. He's got a swagger. He's like a god.
Thor: Ragnarok will be Hulk's fourth appearance in the MCU (not including Mark Ruffalo's Iron Man 3 cameo), and during that time, the only times we've seen Hulk has been when he's unleashed for battle, either intentionally or against Bruce Banner's wishes. As the third Thor movie is partially adapting the Planet Hulk storyline, Hulk will still be fighting adversaries on Sakaar, but he's finally in a place where his might is most appreciated. Hence why he has that "swagger": his power has made him the most popular warrior on Sakaar. That won't last, though, because he'll eventually be pitted against his buddy Thor, and the two of them will later hightail it off Sakaar to stop Hela and the other Thor: Ragnarok villains.
There have also been hints that the MCU Hulk's intelligence is slowly increasing. During the final battle against Ultron in Avengers: Age of Ultron, Hulk boarded the Quinjet and flew off to parts unknown so he wouldn't put Black Widow in danger. It was one of the few times the Green Goliath has been calm, and arguably the first time he was logical. Then last year, Mark Ruffalo mentioned that the Bruce Banner/Hulk consciousness has started to meld a little in Thor: Ragnarok. That doesn't mean that Hulk will be the genius that Banner is, but it does suggest that he won't be nearly as driven by rage as he has been in the past. Keep in mind that Thor: Ragnarok and the next two Avengers movies are said to have a standalone arc for Hulk akin to if he received another solo movie, expect to see some major growth for the green powerhouse in the next few years.
You can see Hulk back in action when Thor: Ragnarok storms into theaters on November 3.