First of all, you have to keep something in mind -- as much as I can appreciate the art of movies, I am not a movie snob. I can enjoy great acting and directing and enjoy B-movies and exploitation films, too. Such films can be good. What's the dividing line? Passion. A desire to make something good, even if you don't have the resources.
James Cameron has scored a major hit with Avatar. And yet, if you listen to him talk in interviews, he refers to movies as "product." No kidding, he used it quite frequently when discussing Titanic and why he made the story choices he did. The story was made to work, but based on external factors the audience would react to, not how the story and characters and situations shaped it. I know lots of people loved Avatar, and that's great. I could only sit there, marveling at how cliche everything happening was, from the whole "great white father coming to save the natives" to the relationships. Consider that, for all the advanced technology, the humans didn't really have anything all that powerful that couldn't be overcome by the native Na'vi. The main bad guys were just cliches -- a corporate type just looking to exploit and a war monger military type. No depth, all you needed to know was you were supposed to boo and hiss at them. Now, the movie at least kept moving (it's actually amazing how it sort of zips along despite nothing ever really being in doubt and it could have easily lost an hour of running time), but the fact is, it was designed by a committee, a committee of public opinion.
Now, let's take a look at Ed Wood. God, I loved Ed Wood. Well, I love the person. He didn't have the money. He didn't have the talent (oh GOD he didn't have the talent). But, like the Tin Woodsman, he had heart. He genuinely wanted to make something good, even if he didn't ultimately succeed. A lot of the things he did are just things every other B movie maker did and still does. I firmly believe that, had he spent a little more time and effort, Plan 9 From Outer Space would have been a perfectly acceptable B movie. Not great, but certainly acceptable. It's this difference that makes me enjoy the Corman version of The Fantastic Four with its B movie feel and $1.4 mil budget far more than the mercinary big budget features with Jessica Alba.
So, Supergirl. What does that have to do with that movie? Supergirl certainly needed some work. But for what it was, it was a perfectly acceptable superhero movie. I sometimes think part of what threw crowds was that the villain was a sorceress. Only us comic book geeks know that the Super family is weak against magic (this was used to great effect in the Justice League cartoon when Superman fought Captain Marvel).
I think what really makes me enjoy the Supergirl movie is Helen Slater's Supergirl. Supergirl was a hero. She screwed up and she went to fix her mistake. Despite being ill-prepared and massively overpowered by her nemesis, she didn't quit, even braving the dangers of the Phantom Zone to save the day. Helen Slater is a heroic Supergirl. By way of contrast, Lauren Vandervoort plays a come-fuck-me-now Supergirl on Smallville. Slater's take is a character you want to root for, to see her succeed, who doesn't dodge her mistakes and responsibilities, but owns up to them and does the right thing. Which is something they don't show often enough in the comic. But I digress.
I can certainly see why people think the Supergirl movie was so bad. But it's like Phantom Planet for me -- it occupies a soft spot in my heart that, depsite every instinct telling me I shouldn't be wrapped up in it, I watch and enjoy it anyway. And I have no explanation or rationalization, it's just how it is.
There you go -- probably the only appreciation piece for the Supergirl movie you will ever read. ;-)