Part of the magic of Star Wars was that it was enjoyable at all ages. The prequels didn't have that. TPM was a kids' movie, AOTR was less of a kids' movie, but it isn't very appealing to adults either. ROTS wasn't appropriate for young children, and it was a mediocre film from an adult perspective.
ANH, ESB, and ROTJ, on the other hand, were/are enjoyable for everybody.