There isn't too much to say about 21 Jump Street other than that it's quite a smart dumb movie, if that makes any sense. It doesn't try to be clever or satirical or too deep. It's just a hilarious film with a ridiculous premise: where two mid twenties cops who go back to high school undercover to root out a drug ring., and all the clichés that involves.
Jonah Hill and Channing Tatum get thrown back into a world they've only been out of long enough for it to change. They both still vividly remember how highschool worked when they were there, but find it not quite going along as they planned. The two of them have a great chemistry, something you really need for this type of buddy-cop feature. As they run, shot and gossip their way through the traumas of popularity and drug dealing they do hit all the traditional plot bumps that these sort of movies do, but it's smart enough to know when to turn a cliche on its head and when to just embrace the cheese factor of it all.
It might just be a rehash of an 80s TV show, but it's really, genuinely funny.