Ahhh Game design, the design process of a game... most of this is decided in numerous meetings consisting of brainstorming with the input of countless ideas till the project leader says ah haa yes i like that.
The ideas are then forwarded to designers to come up with a structure for them and is displayed in the form of Design Document which details everything from the game play to the character designs all the way to story lines.
Right so what is this game play thing that was mentioned? well game play is what it says on the tin its how the game plays mostly considering the consumers experience while playing the game. This may be the interactivity of characters,objects and graphics in short it the rules of the game.
Most of a games design is handled by Game designers and it is these people who are paid to come up wit the ideas for games and define how they will work. However this is not always the case and in smaller company's games design may be done by the entire staff who have their input in the game.
All games follow similar principles but some may vary slightly for example a first person shooter's design document is not going to be the same as a 3rd person strategy game because the game play style is different how ever certain elements may be similar such as storyline for instance and a big example of that is between Halo the new Halo Wars game which follows the same storyline in a sence but has different gameplay.
'What's important for you, when you play?' Hmmmm that is possibly the most annoying question i have ever been asked as i cant give a direct answer to it but i know when i play games i have never been one to pick on a game for its graphics i nearly always however have a go if i think the way the game is layed out before me is rubbish and its the only reason i liked halo so much. The graphics in Halo are nothing special but the story and game play are fantastic so i guess thats what i deem important really.