Silent Running was years ahead of its time, promoting an environmental message. The main character played superbly by Bruce Dern, develops a fondness of his robotic companions, as opposed to his human colleagues. Unlike many of the science fiction films of the era, it lacks dramatic effects, a huge 2001 space opera theme, lasers or explosions. Instead its a much more personal and intimate take of a man faced with some difficult decisions. WALL-E was heavily influenced by Huey and Dewey, as the robots develop unique identities and overcome their limited technology.
Ok so we know that CGI wasn't around in the 70's but that just goes to show that you don't need overblown SFX to make a great science fiction movie. Silent Running has to be the minimalist, gentlest sci/fi film ever and it's fantastic for it. Bruce Dern is fantastic and gives the viewer a real sense of isolation and the relationship between him and the two drones is strangely touching. The end scene will tug at even the hardest of heart strings. I saw this back in the 70's and it's subject matter is still relevant today. If you or you're children grew up watching overblown space/super hero epics, then I urge you to check this out. It may just change your perspective of how a real science fiction film should be made.