German space sim. The titles are X: Beyond the Frontier, X-Tension is an extension for that game, X2: The Threat, X3: Reunion, X3: Terran Conflict, X3: Albion Prelude and the title which is supposed to be released in November is X: Rebirth.
It's a very big universe, has a big background history (though some of that has become less important in the current games), multiple races, and is a great game in general.
There are so many options what you can do in there, you'll hardly ever get bored. You can create a giant industrial empire (with big space station complexes which produce several products, and automated ships transporting and selling them), you can fight against pirates and Xenon or Kha'ak (evil aliens), you can live as a pirate, you can pilot a large fleet of ships or fly a small fighter, you can even work as a police officer (kinda).
A little bit about the background history of the Universe:
The people on earth created an experimental jump gate, for interstellar space travel, which to their surprise connected itself to a large network of other jumpgates. They start colonising planets with terraforming AIs. At some point, because of a faulty update, these AIs go rogue and start terraforming already colonised planets, killing everybody. The AIs are able to increase their abilities in every generation, and became almost unstoppable. When the terraformers attacked Earth a large group of battleships lured them through the jumpgate, which was destroyed afterwards. Through that Earth was saved. There was a large battle on the other side of the jumpgate, and the surviving humans settled there. After a while they forgot about their origins, and started calling themselves "Argon", similar to some of the other races they've encountered on the other side. There is an cephalopod race called "Boron", there is a reptilian race called "Teladi", and there are the humanoid "Split" and "Paranids". These races call the terraformers "Xenon".
X: Beyond the Frontier starts at that point, and you play the first human to reach this area from Earth in almost thousand years. In X2 you play the son of this human and encounter a new alien race which becomes a threat for everybody, the Kha'ak. In the course of the X3 games you finally manage to find a way back to earth. The problem is that the Terrans have become very suspicious of aliens after their experiences with the Xenon, sometimes even to the point of xenophobia.
Edit: Damn, I spend too much time on forums. I've corrected the title of X2. It's called X2: The Threat, not X2: The Thread…
