I saw Forbidden Planet in its original run in a movie theater. I must've been about 10 or 11 at the time. It was the last movie to give me nightmares. I recognized immediately the voice of Robbie the Robot as belonging to the same guy who played Michael Anthony on a TV show of the time called The Millionaire. Even at that age I recognized the cheesy Hollywood style 'romance' that seemed to be mandatory. But I also appreciated that there were some serious, intellectual, aspects to the movie.
A year or two earlier I had seen This Island Earth which was maybe a tad over my head at the time. Not sure now how much I remember from that first viewing and how much from later on. I really liked how the aliens used the scientist-hero's own curiosity to lure him into their clutches. It was more deliberately action-adventure than Forbidden Planet but it did have some intellectual aspects. The aliens were more complex and morally ambiguous than the usual fare, and it had high production values for the special effects. Also, the obligatory romance was better done than in Forbidden Planet.