I said Will's performance is bad because he's trying to be funny in a serious movie, which makes people say he's not really acting, he's just being himself. That's basically due to a bad script. His useless comments (Del Spooner: "You must know my ex-wife"), jokes and all those things make people think the movie is a waste of time because they wanted to see a good (or at least decent) sci-fi movie, and they aren't seeing that at all.
This is the main reason why almost everyone thinks this movie was bad, and with this I mean critics and movie fans with some taste and knowledge about cinema. I don't pay attention to people that say this movie is good because they loved the special effects. If we don't have a convincing performance, the movie can't be good by any means. And no, there was no chemistry between Will and Bridget at all.
Of course each one has his opinion, and I respect it. But sometimes things are pretty obvious...