Transformers 2 was fun. I mean the story is garbage, but it's transformers. If you go excited to see big robots kill each other and have bad ______ surround sound. You won't be disappointed. If you go expecting an oscar worthy movie, stay at home.
I think those are two extremes (a movie doesn't have to be "oscar worthy" just to be enjoyable and avoid insulting the audience's intelligence). You should watch JJ Abrams' interview on Charlie Rose. Abrams is known for big budget action flicks, but he makes a good point that audiences don't care about all that stuff unless they first care about the story and the characters. Special effects have reached a point where there is pretty much nothing they cannot do. Consequently, no matter what is put on the screen, it isn't impressive unless we also can get into the story.