Shazam is a parody....right?

It's much different than the Shazam! TV show on Saturday mornings in the 1970s. The Shazam! TV show was more serious. Also, the Billy Batson in the Shazam! movie is a kid, but the Billy Batson in the Shazam! TV show was older, a guy in his early 20s.

Also, it appears from the Shazam! movie trailer that when Billy Batson turns into Shazam, even though Shazam is older and bigger, Shazam still seems to have Billy Batson's personality. In the Shazam! TV show, Captain Marvel didn't have he same personality as Billy Batson. It was like they were 2 separate people, similar to how Ultraman and Hayata were 2 separate people/beings in the Ultraman TV show.

As for The Greatest American Hero, yes, based on this Shazam! trailer, it has a Greatest American Hero vibe. In The Greatest American Hero, Ralph Hinkley drives out to the desert and is given a suit by a mysterious stranger. The suit gives him super-powers, but he doesn't know all the powers of the suit so he and his FBI buddy have to figure it out. In this Shazam! trailer, we see Billy Batson riding the subway and then meeting a mysterious stranger who gives him the ability to transform into a superhero. But he doesn't know all the powers he has so he and his buddy Freddy try to figure it out.

When I first saw the Shazam! trailer, I immediately thought of The Greatest American Hero. And it appears that others had the same thought, as shown at the 11:45 mark of this Comic-Con panel: