I think Villafan really nailed it in his review when he said that this show had one of the most original concepts ever. They really had something I have yet to see in another movie or television series, and that's very unique in this day and age of constant copycats.
Now if you're reading the reviews, then you are probably already aware of the storyline of Greatest American Hero. Okay, I admit it. Some of it sounds cheesy. But, if you'll buy the premise, it works and it works well. The show is entertaining and sticks to it's premise well. You do also have to get beyond the special effects. Many of them, especially Ralph flying, look bad by today's standards. But if you'll remember it was a TV show from 1981, you'll do just fine.