Pirates of Caribbean a franchise most of us are sick of hearing about, but whenever anyone talks about it the general consensus is curse of the black pearl was amazing. What people also tend to say is how badly the sequels got it wrong but no one ever seems to be able to explain what they got wrong just that they're "not as good as the first" one major factor that doomed the sequels immediately was Captain Jack Sparrow himself, now I know what you're thinking "he's the best part of the movies" and you would be right... to an extent. Jack Sparrow is not the typical hero but that can be explained in three words, he's a side character. Jack never belonged in the spotlight the hero's of the story were always Will and Elizabeth. Jack was just a memorable supporting character who's exact personality that caused intrigue and actual laughs was never repeated after the first one, it was a complete fluke and the studio knows it. Every movie in the franchise after Black Pearl tries to capitalise on Jacks initial popularity, and people keep going to see these movies is in the hope that they capture the magic from the first one.
Now that's not to say the sequels have nothing to offer, the plot threads are explored with both complex and interesting conclusions. Davey jones was a new fan favourite character and the idea of pirate legend such as calypso and a modified version of the Norse kraken, and they expand on the idea of freedom that was so important in the original film. The idea of freedom is perfectly represented in the third movie when the pirate lords (not a good plot point and should have been cut) band together to fight off the British and preserve they're way of life. A strange things these movies do as well is, there isn't a villain. In each movie the main antagonist (no that's not the same as a villain) is sympathetic and has justified reasons for they're actions for example Barbosa from the first film only wants to feel again as he is effectively dead but conscious.
So in the end you can think what you want about these movies don't let some fifteen year old movie geek tell you what to think but I do advise you take a closer look at these movies and try to pinpoint what you like and dislike about each one that way you can appreciate each movie good or bad on a basis better than if its good background noise.