Hundreds of unique worlds, a completely immersive story, truly open-ended gameplay, hilarious Easter eggs, all on a pair of 360k floppies. Yep. They don't make 'em like this anymore.
You start out as a simple spaceship captain. You are given a ship and some funds to assemble a crew and are told to go forth and explore the universe. The plot is only revealed in pieces as the game progresses, and you are free to ignore it completely.
I spent dozens upon dozens of hours playing this game one summer on the old Tandy 1000, a quarter-century ago now. One might ask, "How did they include so much depth and content in 720k?" The answer is ingenious: they used a fractal formula to generate the almost all of the planets, minimizing the storage required while ensuring consistency for each visit.
Unfortunately, I don't think we'll ever see the likes of Starflight again with all our modern technology and interconnectedness. Bah! A thorough treatment of the subject can be found here.