Modern App UI Design tends to favor simple and minimal design aesthetics, with the user interface taking a backseat to let the content shine through and be the hero. The vast majority of modern apps follow this approach.
On the other hand, Video Game UI Design tends to be more stylistic and can be extremely creative, picking up the style and them from the genre of the game. Strong UX Design principles, such as usability and accessibility still heavily apply to both.
If you have a project in mind that you would like to collaborate on, I'd love to hear about it!