Mass Effect
Mass Effect is a science fiction role-playing game series developed by BioWare. The plot centers around a human soldier named Shepard and his/her mission to save the Galaxy from a biomechanical race of the Reapers.
Accodring to BioWare official website of the first game,
The galaxy is trapped in an endless cycle of extinction. Every 50,000 years, an ancient machine race invades the galaxy. With ruthless efficiency, the machines wipe out all advanced organic civilization. They leave behind only the scattered ruins of technology, destroying all evidence of their own existence. Few believe this ancient legend. You, however, know it to be true. The fight to stop this extinction event has become the most important mission in the galaxy.The first Mass Effect game was released on Xbox 360 in November 2007 and for Windows in May 2008. It takes place in the year 2183. Shepard, an executive officer of the Normandy starship, becomes a Spectre (elite agent under the Special Tactics and Reconnaissance) and confronts other Spectre Saren Arterius, who had betrayed good guys and tried to help Reapers during their invasion of the Galaxy. Shepard eventually defeats Saren and prevents destruction of the Citadel, a galactic capital.
The trilogy
A sequel, Mass Effect 2, was released on January 2010, and takes place two years later. The game sees Shepard fighting the Collectors, an alien race abducting entire human colonies. It is subsequently revealed that Collectors are working for the Reapers, so Shepard confronts the machines once again and saves the Galaxy for the second time. How generous of our brave soldier.
Mass Effect 3 is the final installment of the franchise, released on March 6, 2012.
It features improved combat system, new squad mates, multiplayer co-op mode and weapon customization system. In this game, Shepard one way or another defeats the Reapers by suer-weapon called the Crucible. At the end Shepard can choose one of the three options: to control the Reapers, destroy all synthetic life including the Reapers and synthesize all organic and synthetic life together, creating a new life form.
The series have received wide critical acclaim, especially Mass Effect 2, which was called "the Avatar of video games" for its beauty and "everything what people have wanted for the past two-and-a-half years".