Though ostensibly based on the '80s cult TV series of the same name, the new action-comedy "21 Jump Street" also draws heavily on buddy-cop conventions, "Superbad"-style high-school high jinks and the grand tradition of the stoner bromance (see also: the "Harold & Kumar" films, "Pineapple Express"). For all its raunchy familiarity, the film, which stars Jonah Hill and Channing Tatum as rookie cops going undercover to bust a drug ring in their old high school, is charming critics.

Times film critic Betsy Sharkey writes that "21 Jump Street" has "an endearing, punch-you-in-the-arm-because-I-like-you-man charm" and that Hill and Tatum display "great goofball gusto." Both actors — "rock hard" Tatum and "squishy soft" Hill — "bring a kind of vulnerability to their characters that makes whatever mayhem they are up to OK." Sharkey notes that the film is not only about but also created by a buddy pair: Phil Lord and Christopher Miller ("Cloudy With a Chance of Meatballs"), who "clearly understand the push-and-pull and hyper-competitiveness that make guy friendships both complex and stupid."
In the New York Times, A.O. Scott calls the film "an example of how formula-driven entertainment can succeed." Although "21 Jump Street" is "full of the usual boy-comedy stuff" and doesn't break any new conceptual ground, "the whole mess is silly, spirited, and, yes, smart enough to work." Scott credits Hill and Tatum, playing into and against their conventional roles, for providing "the real energy in the film," rather than the run-of-the-mill action sequences.

Roger Ebert, of the Chicago Sun-Times, says "21 Jump Street" isn't a faithful adaptation of the TV series but rather "a mashup of screwball comedy, action and 'The Odd Couple' formula" — and the result isn't half-bad. Ebert commends the script, by Michael Bacall, which is slyly self-referential and "happy to point out all of its improbabilities." Ebert agrees with Scott that the action scenes are a bore; more interesting by far is "the debut of Channing Tatum as an actor who can play comedy. He deadpans so well here he might start looking at Cary Grant movies for remake ideas."

USA Today film critic Claudia Puig is also impressed by Tatum. She writes, "it's no surprise that Hill, as bumbling officer Schmidt, generates so many laughs. But who would expect Tatum, as the dimwitted officer Jenko, to be so comical? More often cast as a standard heartthrob … Tatum holds his own with Hill and every other comic actor in the film."