I guess only Biotron falls under the description of "giant robot," but I believe that Micronauts may have been the coolest line of toys ever made.
I bet one of y'all can answer me this. I remember watching a film on cable about 30 years ago, about a giant robot piloted by a person inside. The guy held a couple of cables and would pull on them to throw punches, etc. It had been dubbed into English, and some of the action took place on one of the moons of a large planet (Saturn or Neptune). It may have been Mazinger Z (based on the little bit I just read about that). This was before I knew what anime was, but I suspected it was from Japan because the drawing style resembled Speed Racer, Battle of the Planets and Star Blazers. I bet someone else saw this on cable the same time that I did.