Space Quest was released by Sierra in 1986, and is one of the best selling adventure games by Sierra. The original Space Quest support a very lame CGA graphics and requires a lot of typing. The VGA version was release in 1991, supports VGA graphics, digitized sound and point-and-click interface.
In Space Quest, we play Roger Wilco, a member of the cleaning crew onboard the scientific spaceship "Arcada", which holds a powerful experimental device called the "Star Generator". Roger emerges from an on-duty nap in a broom closet to find the ship has been boarded and seized by the sinister Sariens.
He finds his way to an escape pod and escapes the "Arcada". After crash-landing, he finds himself on a dry and barren wasteland that is the planet Kerona. Making his way through the desert and through a system of caves below, he is tasked with the killing of a creature called the Orat. He finds the Orat in a cave, and duly kills it.
After succeeding in this task, he returns to the area where he had been given the task and shows the alien that assigned the task to Roger a piece of the Orat. He lets him through a door, and Roger is given a skimmer and the keys.
After navigating a rocky section of the planet, he goes to a bar, and, playing a game of slots, wins a sufficient amount of money so that he can buy a spaceship and a navigation droid.
He does so, and flies to the coordinates (which he overheard from a customer at the bar) where the "Deltaur", the Sarien ship that boarded the "Arcada", is located. After getting aboard it, he infiltrates the "Deltaur" and self-destructs the Star Generator.
As I am a fan of space exploration, I like Space Quest a lot. And if you are also a space exploration fan, and you've never play Space Quest before, please do it now. You will like it.
You can download Space Quest, its manual and walkthrough here.