General consensus is that SM3 will be a better movie (biased on this board of course, but overall I believe to be true given the themes of both movies).
Pirates 2 sucked really REALLY hard. The entire movie made no sense, characters showed no depth of emotion or consistency to each other in the WHOLE movie. I have never been more displeased with a sequel, (including x-men 3). Ex.) Jack Sparrow escapes the pearl on a dingy to the nearby island, yet goes back to the ship because of guilt. However it is specifically said, that the crab only wanted to kill Jack, and not the rest of the crew. So, why did it continue to attack the ship? Makes no sense...
Spider-man 3 on the other hand, closes the themes and ideas of both of the first 2 movies, includes crazy special effects and immense battles. Much better story, much better content, much better movies.
All in all, Pirates will probably win over SM3. Transformers will do as good as Pirates, if not better.