Mentao: My advice, if you are still looking, would be RPG:
Dink Smallwood.
But if you have already played it, then I would recommend
Sentinel Worlds I: Future Magic or
Hard Nova Tarnicus: Hey thanks for these suggestions. Are you Karl Buiter or a fan? I used to have both games when I collected abandonware but never got round to playing them. I notice Starflight and Star Control 2 are mentioned in the wiki entry for both games and I played the crap out of those games in high school and loved them :)
I'm a fan, but I played Sentinel Worlds when I was like 13 years old (around 20 years ago). You have to get used to the interface, but the story is one of the best I've ever played. Later I played Hard Nova which had more or less the same interface.
Regarding Starflight, I've never played it but I did play Starflight 2: Trade Routes of the Cloud Nebula which is another game I would recommend, but I didn't because it is longer and you want a short game. It has a good story, too.