I will start out by saying that "Men in Black 3" is the best of the series so far, at least in my opinion. Why? Well simply because of the depths of the story, it is better planned and executed, and more enjoyable than the previous ones.

The story "Men in Black 3" is about Agent J traveling back in time to prevent an alien invasion of Earth and to prevent the assassination of his partner, Agent K.

Unlike the previous movies, the various aliens in all their strange appearances do not have that much of a prominent part of the movie. Sure they are there, but mostly as background characters. That is nice in itself, because there is still a large range of strange alien creatures to be seen, just in a less active role in the movie. The story in "Men in Black 3" is more character driven, with focus on Agents J and K in particular, and a single alien, Boris the Animal. This does work out quite nicely, because the story takes on a more personal aspect of storytelling, and there is a really, really great moment towards the end of the movie when you learn the truth about the two agents relationship. That was something that I really enjoyed.

Again, you have Will Smith and Tommy Lee Jones returning to their roles, and then Josh Brolin really pulled off stepping into the shoes of portraying a younger version of Agent K. Boris the Animal was also nicely played by Jemaine Clement. And Emma Thompson stepping in as Agent O, new leader of the MIB agency after Zed having passed on.

And as with the previous two movies, the CGI effects in the movie were really great, and the aliens were realistic and believable. Which really is an important thing to make a movie like this enjoyable.

I found this to be the best of the series so far, because it is a more personal story where the multitude of strange alien creatures didn't have a huge part of the screen all the time. And the depths of the plot were well planned and executed, despite the minor flaws here and there (if you read through the 'Goofs' (here on IMDb), but that is really minor details that, I will admit that I didn't notice at all, you'd notice only if you are a, well, a nerd! No offense to anyone. But you really have to be a perfectionist to factual details to notice that, so hats off to those who pointed them out.

If you enjoyed "Men in Black" or "Men in Black II", then you definitely have to watch "Men in Black 3", because it adds a lot to the overall storyline of the MIB universe.