As has been noted before the acting skills and technical aspects such as camera work, editing and audio are so good in "Hollywood" productions that they can for the short term distract attention from a weak script. Look at Miami Vice sometime. In a lot of cases those episodes don't hold up simply because the scripts were weak. On first viewing, the camera work, the stylish sets, the beautiful clothes and overall atmosphere created by the flashy editing were enough to call attention away from the fact that the scripts were full of holes...
I don't agree. We're talking about the difference between competent and not competent. In Maurice's thread on writing he talks about things like three act structure, etc. - the people making a movie like Transformers II at least get this kind of thing right; most fan films don't.