I'd guess there's anywhere from two to three times more jokes in 22 than there were in 21 Jump Street. That ends up making the sequel feel about a half-hour longer than the first film, even though its runtime exceeds that of the first by less than ten minutes.
It suffers from a pretty intense case of diminishing returns: three jokes aren't necessarily better than just one, if the one joke is really funny. I laughed through the movie's entire first half, and was ready for the movie to end right around the 3/4 mark, when my stream of laughter had slowed to a trickle, and laughing out loud had turned into guffaws, and then chuckles, and then just blowing air out of my nose.
When Miller and Lord aren't able to surprise, they settle for being able to entertain. While the movie is thoroughly entertaining, filled to the brim with jokes and gags, it never manages to catch you off guard like the first movie did.
Some of that just comes with the territory of being a sequel, but it makes it ironic that, in insisting the sequel is exactly the same thing as the first movie, it ends up being an entirely different kind of thing. 21 Jump Street had six or seven absolutely standout moments, and was generally entertaining in between those segments.
In contrast, 22 Jump Street is always pretty funny, and occasionally very funny. But the sheer amount of noise at play means that nothing stands out quite as much, nothing lands as hard, and the film settles for being generally good rather than occasionally spectacular . . .
. . . Which is exactly the joke, made over and over again. There's very little to say about 22 Jump Street that Miller and Lord haven't already anticipated and critiqued about themselves, within the film. Watching the film anticipate the criticisms people like you and me would level against it—and even respond to them—makes for a fun meta-level movie watching experience. But it starts to wear a little thin towards the end, where critical gamesmanship starts to feel a little bit like insecurity. A project like The Lego Movie suits the duo infinitely better, where they're not being forced to make excuses for themselves, where the film can just stand as itself without having to talk about itself too much.
There's not too much to say about 22 Jump Street—or, that is, there's not much to say that Miller and Lord haven't already said inside the movie. Something I haven't mentioned yet is the movie's persistent irreverence and crudity, including a whole bunch of language. This shouldn't come as a shock to anyone who's seen the first movie, but in case it's unclear: I can't recommend this movie to anyone who can't withstand extensively crude jokes, often to the point of being unjustifiable.
But I guess the only difference between 21 Jump Street and its successor is that I felt conflicted about not being able to recommend the first to some Christian audiences, because the movie as a unit was so exceptional.