The surprise in Grudge Match, the not-quite-a-comedy that pits Rocky Balboa against Raging Bull, isn't that it has the chutzpah to posit Sylvester Stallone and Robert DeNiro as equally matched rivals. The surprise is in how easily audiences will buy it. For years, DeNiro has slumped through godawful comedies where he seems to work about as hard as a high-school coach teaching health class. Now the greatest of street-tough '70s Noo Yawk film actors has sunk to the level of Stallone, the most ridiculous of that breed. An even bigger surprise: Despite the scene where DeNiro's retirement-aged pugilist farts on his trainer, Grudge Match aspires to be more than some Jack Lemmon/Walter Matthau-style dispenser of prostate jokes. Director Peter Segal is aiming for nothing less than the third-best boxing movie these guys have ever starred in. The stars play old rivals goaded by a promoter (a cartoonish Kevin Hart) into one last late-in-life fight. Director Peter Segal's gearbox gets jammed between recession-era sports drama and brainless comedy, especially as Hart hollers pop-culture punch lines like he's the squirrel sidekick in a CGI kiddo flick. Credit Segal with this, though: He elicits an engaged and engaging performance from DeNiro, who seems to mean what he's saying even when he's forced to exult, "I'm having the time of my life!" Stallone, meanwhile, is ripped, as always, and his face has pinked as it's settled into slack immobility -- his eyes and mouth look like holes in meat. He plays the relatable one, the everyday schlub. But what's the point of a movie about an everyman aging whose star has done everything in his power to look like he hasn't?