I also dont think that childhood bond/love is always everlasting in movies..You see it in many stories that the first love is not the right love...
T&T could have changed it and made Elizabeth follow what appears to be her heart sicne before she even met Will Turner but instead they thought they would use the same pattern with movie 1 where Jack is actually just shoved there to make the W/E relationship stronger by the end of it all...but a bit of a mistake to split the story into 2..because it now looks as if the pattern for DMC works much better and rakes in the $$$..and this is where Jack actually IS the main love interest...and appears to be winning the girl himself..
and what pisses me of..jack gets rather emotionally hurt by Liz in both circumstances
only this time she shows guilt for it whch she has never done in the past when it comes betraying Jack or Norrington or all those sailors