I saw Men In Black II over the 4th of July weekend and was quite a bit disappointed in how much energy, effort, and money went in to something so completely devoid of a story.
Walking away from the theater, I realized what I had just seen: A spinoff show. You know those lackluster shows that follow some previously interesting, but somewhat minor character in new situations and new locales? They're rarely half as good as whatever spawned them, and usually for obvious reasons.
MIB 2 was held up by a few characters that had brief amusing parts in the first film. That talking pug that got a shaking in the first film? He's funny for about 30 seconds in both films but shows up as Jay's partner for a number of unfunny sequences. The pawn shop alien who gets his head blown off? He gets a much bigger scene this time around. I barely remembered the worm guys from the first film, but they're given full supporting roles in this one.
I bet it goes like this: take a quirky film that grossed way more than you thought, and take the cash cow to sequel with as little creative work as possible. Instead of a script, start by turning every funny 30 second cameo by an interesting character in the first film into five minutes with the stars. Sprinkle in pre-paid product endorsements and placements liberally, then tack on love story to fill out the remaining minutes.
Overall it was way too much computer generated sets and action with very little plot and character development. It's hard to care about anyone in the film and the whole thing seems like Wild Wild West: plenty of nice looking CG work sans a story to hold any of it up.