I absolutely loved Starflight
while I was growing up. It had combat, but it was more in the style of the 60's Star Trek; your primary mission was exploration and to stop a galactic threat, but you would run into other ships in the void and have to deal with them. You could often work things out diplomatically and not even have to fight; but there were races who wouldn't even talk to you (though I do remember getting the Uhlek to talk to me one time - it was just one brief statement like "Prepare to die" or something and then they cut it off).
I haven't tried any of the other games mentioned, but I would love to find something like Starflight again.