I agree to a point Daniel. There's nothing inherently wrong with adaptations or the borrowing of old ideas to tell a story, it's done all the time in any given form of media from comics to music to the big screen itself. The problem I have is when this is done while disregarding the effort required to make something good.
Fact is, there are some really bad movies out there. Some so awful you wonder how any production company could let them happen. I'll admit, seeing some of these stinkers had turned my perception of the last decade or so of movies sour, and left me rather critical of any films I choose to see, yet I still try and give these creations a chance.
Any successful franchise has the potential to be picked up by someone in hopes of making a movie. For years anime had only a cult following through fansubs and the rare series to be dubbed every once in a while. Then in the late 90s it hit mainstream with network attention to series like Pokemon, DBZ and the Toonami lineup, and more series began to see releases outside of Japan. Now, like everything that exists, people are pondering the live action adaptations of these and just starting to churn some out.
I'm not saying they're all going to be bad movies, but the reason they're being made is because they have a strong audience. If someone had gone up to a production company with the script for the Dragonball movie in the early 90s he would have been tossed out the door. Now Hollywood sees cash potential, so they greenlight it. But they're not the only ones, writers, actors, directors and so on see cash potential too. Whether they're any damn good at making movies or not some people in the business don't care. They can make the worst adaptation of a franchise possible, and are still guaranteed money because of the name alone.
You are right though, some people take too much flak for their work. I agree with you about Michael Bay, and frankly loved Transformers and the new Friday the 13th movie. I'll probably wind up seeing the new X-Men movie and definitely see Revenge of the Fallen as well.
On a final note, a Spielberg directed GitS movie does actually sound somewhat promising. Stating most of what he directs turns to shit was a personal opinion, even then there are some of his directorial works I've liked (Indiana Jones pre-Crystal Skull) Hopefully they can put something together that captures the psychological elements of the series as well as the futuristic action, and not just a gigantic CG-fest.