Hulk's return in Thor: Ragnarok is triumphant. Having developed his fighting skills as a gladiator (and his comedic chops), the big green guy stole the show in the third Thor film. His appearance drew from the Planet Hulk storyline, though admittedly they left a few of the less-jubilant details out.
Planet Hulk plays out like a big green Greek tragedy. Hulk's exile is entirely involuntary. He's lured onto a ship by the Illuminati (comprised of Marvel Universe masterminds like Professor X, Tony Stark, and Mr. Fantastic) and launched into space, with the vessel programmed to take him to a peaceful deserted planet. Instead, he ends up in a wormhole that takes him to Sakaar, a brutal world where gladiator slaves are forced to fight to the death. He ends up rising through the ranks as a gladiator and then stages a rebellion, soon becoming the de facto benevolent ruler of the planet alongside a surrogate family and the woman he loves (and is carrying his child). But the spaceship that took him to Sakaar explodes and kills his wife and his city, sending Hulk on a brutal path of revenge back to Earth.
Given Ragnarok's tone, it makes sense that none of this made it to the screen. It's a pretty dark story to adapt to the MCU to begin with. The franchise has never shied away from somber moments, but Planet Hulk may have been too much of a downer overall to adapt properly.