What Megan Fox destroys with poor to nonexistent acting, she makes up for in looks.  Shia LaBeouf is a better actor for sure, but he doesn't have as much backup as Fox does.  He's annoying.  
I enjoyed the second film more then the first, mainly because the bot battles are brought up a notch.  In the end, it's about the transformers and not the people that go along with their schemes.  I wouldn't care if they replaced all the actors (the ones playing people).