Some additional Notes

Explosions push objects and players back, players run and jump in a more realistic way, and when directly hit with a rocket, enemies explode into giblets (or "gibs," as the gaming community calls them) of flesh. These new physics not only made gameplay more realistic and immersive, but also created potential for players to experiment in ways that the designers had not expected. Rocket jumping was one tactic that emerged. The player jumps while firing a rocket straight down so that the explosion propels him farther into the air. The game development community began to realize that giving players some simple physics-based mechanics lets them experiment with the game and experience it in ways that had not been possible before. Other PC games like Camageddon (1997) and Die by the Sword (1998) further pushed the available hardware to generate believable physics.

Nintendo was clearly adept at rendering physics in ways that made its games engaging. The recently released Super Mario Galaxy is a testament to Nintendo's ability to continue pushing the envelope in that regard. Galaxy features globe-shaped levels that have gravitational pull so that Mario can run along the underside of the globe without falling into space. By manipulating this mechanic in every way possible, Nintendo has again given other game developers a lesson in how to use physics to create successful games.

How physics are implemented in a game determine what style of gameplay the final product will have, whether it's a true-to-life simulation or a fantastical experience.

from: http://www.gamecareerguide.com/features/534/physics_in_mass_market_.php?page=2

Stories work best is in their ability to provide a context for what the player does. The story should answer the question, "Why am I doing what I'm doing?" It's the frosting that makes good cake even more delicious. For example, without GLaDOS' clever voiceovers, Portal is still a fun game. Throw in that extra layer of storytelling, and suddenly you've got a game of the year.

Furthermore, story can add an emotional weight to a game, making it more relevant to players. The Final Fantasy series is an excellent example. Without the emotionally driven, high fantasy tales at the heart of these games, they are still decent enough role-playing games. But the well-crafted stories that provide a context for the weapons, characters, stats, and combat have created a top-notch franchise. In this way, story answers the question, "Why do I care?"

from: http://www.gamecareerguide.com/features/536/three_novice_mistakes_in_game_.php?page=1