Space Quest II: Vohaul's Revenge (Sierra On-Line, 1987)
With more plot and better characterizations, Space Quest II is certainly worth your time if you enjoyed the first Space Quest or if you enjoy more unconventional science fiction. It is not much harder than the previous game (actually, it might be easier), and has a plot that succumbs too easily to the silliness pervading the characters and an ending that is somewhat predictable. Nevertheless, this is an enjoyable game that has a good amount of color and interest of its own, in addition to what it gained by being spawned from Space Quest.