I walked out of Richard Donner’s newest movie, “16 Blocks,” sure that I didn’t like it.

I found the message cliché, the plot twist toward the end tired and the whole film an exercise in empty, feel-good entertainment.

The plot takes little to sum up, which is perhaps part of my complaint: A downtrodden alcoholic cop (Bruce Willis) is assigned to take a small-time crook (Mos Def) to a grand jury hearing that is – you guessed it – 16 Blocks away. Along the way, as Willis faces police corruption and takes on superiors, the crook changes the cop’s life.

To be sure, there are funny and even tender moments in “16 Blocks,” and Mos Def succeeds in winning the audience’s heart. But what impressed me most was Willis.

I was certain this was going to be just another Bruce Willis movie starring Bruce Willis as Bruce Willis. I struggle enough to like Willis as it is: His politics are all wrong, and I’ve seen him play the tough and tortured, squinty-eyed, cynical, quasi-Bogart police character in enough movies. He’s good at it, but when that’s the only character you play, why wouldn’t you be?

Donner has managed to break him out of this mold somehow. We still have the tortured, hard-drinking cop. But here we have a raw edge that makes it seem real. Willis is pot-bellied, balding, unshaven, mustached and limping. In short, he looks terrible.

And Willis doesn’t run his normal shtick. He gives no tough-guy one-liners to the beautiful girl about how he has no strings. No wife who has left him, no kid he has killed in a standoff gone bad. He’s just a dejected everyman who has been sucked into a system that has worn him thin, and in much of the movie he conveys this without saying a word, but by simply looking pathetic.

That’s part of what makes it real: Willis’ Jack Mosley isn’t down on his luck because of any one all-encompassing failure or rejection that now defines his life. He’s just stuck, like many people, in a life that runs him, instead of the other way around.

Mos Def is comic relief, and the film’s redeeming presence. Yes, it is cliché: The reformed crook is the good guy, and the cop is the one who has to change. And that, of course, is the film’s main message: That people can change.

Really? Who knew?

The thing is Willis, Donner and Mos Def (which sounds like a great title for a Christmas album) sell you on it. After seeing Willis’ character at the beginning and then at the end, you somehow feel good despite yourself. You see Mos Def’s sincerity, and you believe it. And you walk out of the theater with a renewed sense that life can change, you can change and things can be different if you want them to be.

Cliché? Yes. Profound? Perhaps not. But sometimes we all need little reminders of life’s truisms, of the maxims your mother always told you.

“16 Blocks” won’t change your life. But it might help remind you that you can.