Here comes some good quotes from the book Game Interface Design. I believe they are essential ideas to assist the process of creating games. Let's check these points.
Even more important than the visual aspect of interface design is the funcionality. A poor interface can ruin the entire video game experience. The game experience will be negative if the user is confused and can't figure out how to navigate the front-end menu or if he can't understand where to find information while playing the game. (page 2)
Interface planning helps game design. A detailed plan for a video game interface can really help drive game design. Fleshing out all of the details in the menus and the HUD (heads-up display) will force many game-lay decisions to be made early. (page 10)
Simplicity and organization should still be your design goal. The user will enjoy being able to look at a screen and instantly know what to do. Keep your design simple. (page 69)
FOX, Brent. Game interface design. Boston: Thomson Course Technology, 2005.