Something like Escape Velocity?
(Escape Velocity Nova, latest entry in he EV series, works on OSX; http://www.ambrosiasw.com/games/evn/ )
I would really like to get hold of Drelbs again but cannot for the life of find out where. Thank you.
Sun-Dog is what came to mind for me. You had to out fit your ship with special modifications and do missions for a colony including finding cryogenically frozen colonists around the various solar systems
My favorite was the Ultima series. I played Ultima III to IV. The Jump from 4 to 5 was huge with the eight virtues and whatnot. I also thoroughly enjoyed the orginal Bard's Tale!