I have always wondered why Captain Marvel AKA Shazam wasn't a bigger hero. The dude has a whole array of powers, a mythology, and a supporting cast... but this series perhaps begins to shed some light on the characters' limited appeal. While the Cap and Mary are fine enough, Uncle Dudley, Tawky Tawny and Captain Marvel Jr. each have some strange quirks that were probably exacerbated by this low budget / effort production. And there was just a silliness to the Fawcett world that makes The Big Red Cheese more of a parody or kids' hero than a bona fide DC powerhouse.
Lets start with the tiger. What is Tawnys deal anyways. He seems like such an odd character to be included in this series. I am not even referring to the talking tiger aspect. Just in general, he doesn't really do anything other than just hang out with weird Uncle Dudley who is himself pretty useless. And why does Cap Jr say "Captain Marvel" to transform? I am sure there is a reason, but this series didn't attempt to address it even though it was a plot point.
As for the villains, I did enjoy Black Adam and Mister Mind to some degree, Star Master had a great design and Dr. Sivana was fine I guess, but the other villains were mostly just bizarre and forgettable. This is going to be one of those series where I really can't pick a top 5. I will say watch Black Adam's Return to get a flavor for the show and cut your losses. Hopefully some day the heroes will get the treatment they deserve.
As for the three crossovers, they were pretty pointless but Girl of His Dreams gets points for being the best offering and for also possibly spawning an urban legend of a long lost episode of Shazam!