Games Design, a pretty big topic, and with it comes a great deal of responsibility, if you don't have a good design you're not going to get much out of it. In a modern day game development company (obviously this is dependant on the size of the company and project) there would be a team of designers working together closely. Then this team would branch out into a number of areas such as lead designer, sound designer, level designer, character designer and so on. One quality all designers need is good communication, as the communication of ideas is what they do.
There are many stages to the games design process. These are started off by choosing a goal and a topic for which to base the game around. Then much research and preperation is done. The designer must immerse themselves in the topic, finding out information, details and anything relevant.
Next comes the design phase. This is divided up into three sub-sections.
I/O Structure - This is 'the system that communicates information between the computer and the player.' this includes everything from graphics to input method.
Game Structure - This is 'the internal architecture of causal relationships that define the obstacles the player must overcome in the course of the game.' So how to make the goal and topic into a workable system, and how the game would operate eg. how you would shoot/fight, and the tactics involved in these operations.
Program Structure - This is 'the organization of mainline code, subroutines, interrupts, and data that make up the entire program.' This structure is the vehicle which translates the I/O Structure and Game Structure into a real product.
All three of the structures must be created simultaneously, for they must each work together. Decisions made in one structure must be checked to see how they react with the other structures.
Now gameplay could be a term to describe how all of the above terms work and what experience they give you. A dictionary states that gameplay is the:
'Ambiguous term for the total effect of all active game elements. Refers to the holistic game experience and the ability of the game to command the attention of the player.
There are a number of things that are important to me when I play games, but i guess it depends on what sort of game I'm playing. For example if I'm playing a shooter, I prefere it to be realistic and a bit tactical. Even little details can win me over, such as if a character breathes heavily after sprinting of if the camera shakes when something explodes. What really impresses me is if a character moves realistically, reacting to the environment and whats going on around him/her.
One game that I thought did this well was Tom Clancy's Ghost Recon: Advanced Warfighter 2
But at the end of the day, no amount of realistic movement or camera shaking is going to get me to like a wrestling game.