On Stranger Tides was much better than 2 and 3... 1 and 4 are tied in my opinion with a 4.5/5.
I found the plot easy to understand, but with enough twists to keep me entertained. The acting was excellent in my opinion. Angelica's character added an interesting thread to the plot. I think... ah... the mermaids could have been a little less creepy. Although they didn't bother me really. Oh, and I want to know what happened with the preacher guy.
I'm planning to pre-order On Stranger Tides. Can't wait until autumn when it'll get here!