The star system for MIB3 is simple. How much have you like the other two in the series. As with everything in life it depends what you like. I'm a fan, The first was superb the second good and this one was slightly better. The storyline is interesting throughout and as others have said Josh brolin was excellent. Jermaine Clement gave a good performance but I thought the same about him as I did Tommy Lee Jones, the movie would of been even better had they featured more.
Definitely worth a watch and another excellent movie from Wil Smith.