Similar to how the Batman franchise spun off Catwoman, after three Christopher Reeve movies, the Superman franchise spun off Supergirl. However, while Catwoman was basically made because the next proper Batman movie was in development hell, my understanding is that Supergirl was a pure spinoff attempt riding on the success of Superman. While Catwoman is generally considered awful, it was followed by the acclaimed Dark Knight Trilogy, and I get the sense Supergirl is considered okay but forgettable, and it was followed by Superman IV.
I know exactly what to expect from the plot because this is the introductory movie of a superhero, which has been required to be the rote origin story for around 40 years, if not longer. As for a villain to slot in, I’m not sure what to expect, since I don’t know of Supergirl having any villains that are “hers”. I’m really not that familiar with her at all besides the basics of her relationship with Superman, so maybe I won’t have lore bogging down my enjoyment.
A large-budget film with a star-studded cast and strict attention to period accuracy could go poorly in all sorts of ways. The actors could fight for attention to the detriment of the film, the visual appeal could be lost in gritty details or vice versa, and the effort put into the enormous practical concerns could stomp out any entertainment value of the film.
These worries are only enhanced by the subject material. I vaguely recall an adaptation of The Three Musketeers in that a young man wants to be a Musketeer, gets in a fight with some, and then they all have adventures together. Rather dull, especially if one isn’t into swashbuckling tales.
I recognize many names, but I can connect hardly any of them with anything I know. At least it’s sold as a comedy, but I don’t expect much out of a 70s film.
Usually, I avoid sequels, but this pair was intended to be a single film, so I am taking it as one.