these days, when you talk about fantasy films with superheroes, there's just got to be CGI in it. I'm not against it because unless someone can make a human fly or suit up a man in highly intricate robot costume, i don't see any other way to portray such scenes without making the audience feel like they're watching a carnival show.
The problem comes when the CGI overshadows the storylines (transformers 2) bad actors (Megan Fox) and just flawed story telling that never really delivers you that feeling of satisfaction, like you want to retell the whole movie to your friends even though you already know that they've seen it.
CGI is there to help, but it would never surpass the importance of a good storyline.