The Watch isn't a bad film, but it isn't what it secretly yearns to be. What it really wants to be is "Ghostbusters," but it is in tone a bit too mean spirited for that. Tone is always a bugger when writing a film. It is just one of those things that is a magical combination of actor, director and script that really can't be predicted. Sure there's a lot of snark in "Ghostbusters," but when Bill Murray did snark (at least at that point in his career) there was a twinkle in his eye that made us forgive him totally. There is no such twinkle in Ben Stiller's eye (no doubt killed by Focker movies) nor Vince Vaughn who I believe was born without a soul.
The story is simple. A naive little town is being invaded by the most generic aliens not imagined. Ben Stiller is a go getter and club maker so after the first mysterious death it's only natural he starts a neighborhood watch program. The only takers are a bunch of losers who use it as sort of a man's club slash macho tester. Everything else is basically clockwork.
Now this isn't a bad film, it's just two shades above bland film. You can watch. You can smile here and there, and then forget it. Definitely forget it.