Okay, I'm not going to lie, I haven't seen MIB III and I hear that it doesn't suck but MIB II sucked enough that I can't quite bring myself to watch it. But here's the thing: they waited too long to make a shitty sequel and then waited WAY too long to make a non-shitty sequel. Men in Black came out five years before MIB II. There was then a ten-year gap between the second and the third film. The two good movies in this series are fifteen years apart and (and holy shit, Men in Black films have been made in every one of the last three decades, what the fuck is wrong with us that we're taking so long to do this?) that's too long to hold on to a core audience.
Men in Black is an immensely diverting movie. It's goofy fun with silly aliens and a ridiculously accelerated plot and cool montages involving identity erasure and putting on suits. But it also does a great job of building up an easy-to-swallow world that's full of fascinating possibilities.
Tolkein took thousands of pages to build a world we all want to hang out in. Herbert took thousands of pages. The Star Trek universe has been built up for half a century. Men in Black built the universe in just under two hours and we still haven't even scratched the surface of the fun that could be had there. (This is, of course, discussing only the cinematic universe. I'm completely aware that the comics have been doing it for a long time but the approach to the content and morality of the comics makes the print and cinematic universes totally different canons).
So I watched Men in Black tonight and I had fun with it. I really appreciated the absurd physical comedy Vincent D'Onofrio put into his performance. It's entertaining as shit to watch Will Smith butt heads with Tommy Lee Jones and to watch them both be different kinds of awesome. There are cool aliens and a kitty and nice explosions and pretty much everything about the movie is entertaining - I just wish there had been a better follow-up to a movie that had so much potential.