Elite and Elite II, played them both, however I give the nod to the Wing Commander series and specifically Privateer for one simple reason. They did not making flying difficult let alone everyone's badge of honor in Elite in making your first successful docking with the rotating stations.

Still my favorite space game ever had to be Starflight though Starflight II came close. Not the same play style but early games on computers during that time were such a marvel for how much they did with so little