Men in Black was not a movie that needed a sequel. As a stand-alone movie, it was great, but it made a shitload of money at the box office, so a sequel was inevitable. Waiting five years for this was a huge deal, so naturally this film was a hugely anticipated one. When people saw this in theatres, a great many walked out disappointed. I can see exactly why. Men in Black II isn't really a bad movie, but it's still a colossal disappointment for a sequel to a movie as popular and memorable as Men In Black to be just mediocre. It just feels like a reheated, less clever version of the first movie that borrows stuff from its predecessor with mixed results, like the consensus said.
MIB2 takes place five years after the original, with Agent J (Will Smith) now working with the over-emotional Agent T (Patrick Warburton). Agent T is just a sorry excuse to get Tommy Lee Jones back and we are glad when he finally does get back. J is called to investigate a murder of an alien at a pizzeria and he meets Laura (Rosario Dawson), who he starts to have feelings for. Serleena (disguised as Lara Flynn Boyle), an alien plant (that just looked like a less cool version of Audrey II from Little Shop of Horrors) is looking for a light (that happens to be on a bracelet belonging to Rosario Dawson, another element from the first movie) and if the light is on Earth too long, Earth will be destroyed. This also involves K getting his memory back (if you've seen the first movie, you'll understand) and the secret of Laura.
I won't give anything else away, but this film's story is okay. The jokes are much less fresh than the original and while still being sporadically funny, are much more silly. The jokes are also based more on running gags and one-joke characters, like the running gag of Tony Shalhoub's character getting his head blown off. There's also Johnny Knoxville and his second head, and the...eh villain of Lara Flynn Boyle. I do like Frank the Pug though, just because I really love pug dogs and he's pretty much the only talking animal that still amuses me. He is a one-joke character, but a one-joke character that I really enjoy.
Smith and Jones still work well together, despite their diminished script and diminished jokes. I still can't see anyone but them playing Agents J and K. Rosario Dawson is okay, and she and Will have okay chemistry. Lara Flynn Boyle is...eh as the human personification of Serleena, and the rest of the performances range from average to eh, so we'll be moving on. The special effects, however good they are, make the movie suffer from CGI overload which could kill it. The designs of the aliens also aren't as creative as the first movie, even if they are wonderfully CGI'ed (if that's even a word). The action is okay as well, but again, it just feels like a mediocre rehash of the first film.
All in all, watch MIB2 at your own discretion. It still has all the action and special effects of the first movie, but what it's lacking is the sense of humour, heart, and outright coolness of the first film. Maybe the third film will be better, but I hope with it they will at least try a little harder and let this just be subject to middle-child syndrome. It has its moments, but MIB2 just ends up being mediocre and disappointing, copying the first film with mixed results. If you saw and liked the first movie, watch this one just for completion's sake, but prepare to be disappointed. If you haven't seen the first movie, check it out and watch this one based on your reaction to the first film.