The Ur-Quan Masters is probably one of the most fascinating space games I have ever played.
You start out as some guy on with a space ship and fly back to Earth only to be greeted by a probe vessel of the Ur-Quan. It tells you to stay where you are to get taken into custody since your ship doesn't have a license plate or something. If you disregard this and instead try to enter Earth's air-space you will find that it's enveloped by a red shield that won't let you through so you ask on the space station near Earth why you cannot enter Earth only to learn that the Ur-Quan enslaved all of humanity. The commander of the space station asks you if you want to free humanity from the Ur-Quans' grip and of course you agree. This is where the fun starts.
The commander asks you to go to different planets to gather minerals (which you can trade for space credits) to upgrade your ship and buy smaller ships for fighting other ships. He also wants you to find allies for your cause, since there are quite a number of oppressed races that hate the Ur-Quan. You talk to a lot of people, and being disrespectful isn't always the best course of action.
Battle is being controlled simply with the arrow keys to steer and ctrl to shoot. Many different space ships offer different attack power and maneuverability. A ship is considered destroyed when all crew members are dead.
What I like is the huge lore. The captain fills you in on the different races and their function in the big war that happened before. The races you meat can either be very silly or threatening. Travelling through space is fun because there are a lot of places you can travel to, so finding a certain race by chance is especially exciting.
Definitely a good game, and the best part is that it's FREE!