So, Who Embarrasses Himself The Most In Rock of Ages?S

The central appeal—or anti-appeal—of any Hollywood adaptation of a musical is not about the music or the choreography or the set pieces; it's about watching actors who don't usually sing, sing. One of the most fun aspects of Chicago was learning how charming and deft Richard Gere was; it was equally enlightening to learn just how awful of a singer Julia Roberts was in Everyone Says I Love You. This maxim is perhaps best illustrated in Rock of Ages, opening Friday, which features a scroll of Big Name Stars floofing up their hair, pretending they know how to headbang, and warbling Twisted Sister and Skid Row songs. It's high risk for all these stars, with little tangible reward: If it works, well, surprise, Catherine Zeta-Jones and Quiet Riot go together after all, and if it doesn't, well, you just have fat Alec Baldwin bouncing around to REO Speedwagon.

Since a conventional review of Rock of Ages seems a bit beside the point—in short: it's super cheesy, it thinks Journey and Starship are somehow "rock," it is way way WAY too long, and, after all that, some of these songs are still sorta great, even when sung by idiots who had no idea who Bret Michaels was until his reality show—I thought I'd just go through actor by actor and rate them on how they did, how much they embarrassed themselves, if at all. From my experience, when it comes to these movies, that's all anyone really wants to know.

I'll rank them from 0 to 10, 10 meaning "holy shit, this guy should take over when Eddie Van Halen inevitably murders David Lee Roth" and 0 meaning "likely never able to show one's face in public again." Let's go to it.

Paul Giamatti. Pig Vomit plays a sleazy record executive who is the movie's lone real villain, because he is THE MAN, MAN. He sings on only one song, "Here I Go Again," and just a couple of verses at that. Director Adam Shankman has saddled him with a ridiculous ponytail that does him no favors, and you can make an argument that Giamatti these days is acting almost exclusively with his neck. Also, it's not nice to make a Yale School of Drama scholar and multiple Oscar nominee spend most of a movie providing reaction shots to a monkey. Rating: 4.

Russell Brand. Listen, I'm glad Russell Brand is happy and sober now, but honestly, Brits, explain this to me: This guy was actually once considered dangerous? His out-of-control rockstar schtick has never been convincing, and it's particularly galling here, considering this supposed "rebel" expends considerable energy belting out "We Built This City," which very well might be the least rock 'n' roll song of all time. Honestly, I keep waiting for Brand to display a talent past "fitting into tight leather pants at the age of 37." (No small feat, that.) Rating: 3

Mary J. Blige. The "No More Drama" hyphenate—who has become so big she now has her own best-selling perfume—plays the manager of a strip club, but she's really not here to do anything but sing the shit out of some fuckin' songs, because she is Mary J. Blige. She does this splendidly, being Mary J. Blige, though the cognitive dissonance of Mary J. Blige pouring vast dollops of soul into a Whitesnake song still has my teeth vibrating. Rating: 9.

Catherine Zeta-Jones. So slinky and fun in Chicago, Zeta-Jones has the role of the drip Tipper Gore stand-in, the wife of the Los Angeles mayor, a woman who tries to ban rock 'n' roll because there's Just Too Much Sex. It's a dumb part, and Zeta-Jones can't do much with it, particularly in a groaner of a scene in which she finger-guns her way through "Hit Me With Your Best Shot" while dancing through pews at a church. She exists because this movie needs a plot, I guess. (Wait, does it?) Rating: 4.

Julianne Hough. I'll confess, I've never seen this woman before in my life; apparently she was on a reality show. Anyway, she's got a nice voice, she's physically attractive, she seems game for anything, and I'm pretty certain she'd never heard of Axl Rose until this movie. (And maybe not still.) Rating: 6.

Bryan Cranston. Walter White plays the mayor, Zeta-Jones's husband, in full-on mugging Malcolm in the Middle mode. At one point we get a closeup of his tight whities as his mistress spanks him with a ladle. Yikes. This is definitely not the one who knocks. I'm just gonna try to forget he was even in this. Rating: 2.

Alec Baldwin. Baldwin reportedly tried to get out of this movie at the last minute but was contractually obligated to say on. I can see what he was thinking. Baldwin's too naturally skilled a comic actor to be terrible in the role of Dennis Dupree, the beleaguered rock club owner, but costuming him in a ridiculous wig and, worse, extremely tight clothing does him no favors. He spends most of the movie looking like a puffy, swelling, perhaps infected Muppet. Rating: 4.

Malin Akerman. As a Rolling Stone journalist assigned a feature on rock god Stacee Jaxx, Akerman gets several opportunities to show off her underrated comic chops—she's consistently funny on Rob Corrdry's Children's Hospital—including a bravura sex scene with Jaxx on a billiards table that manages to be both goofily erotic and a little terrifying. (At one point, I thought Akerman might possess multiple tongues.) If anyone gets a career boost out of this movie, I bet it's her. Rating: 8.

Diego Boneta. A brief Wikipedia scan informs me that Boneta was on a Mexican soap and is on some show called Pretty Little Liars. I can say with utmost certainty that has never, ever touched an electric rhythm guitar before this movie, and it's possible he'd never seen one. He is less convincing playing a young metalhead than he would be playing a stalk of celery, or a duvet cover, or a Cuisinart. No one has ever said "I Wanna Rock" with less conviction. Boneta, to put it mildly, is a stiff, and it's pretty telling that when Giamatti's exec signs him to a contract and makes him cut his hair and join a boy band, Boneta looks more comfortable than at any other point of the film. At one point, Boneta refers to Lemmy from Motörhead, and it's like watching someone urinate on the floor of Saint Peter's Basilica. Except that would sound better. Rating: 1.

Tom Cruise. I had to save the guy everyone really wants to know about for last. This'll come as a surprise, but it shouldn't: Cruise is without question the best thing about Rock of Ages and certainly the only reason to see it. As Stacee Jaxx, the aging, "tortured" oversexed rock god, Cruise isn't convincing exactly—it's tough for anyone who legitimately loved Def Leppard as a teen to listen to Cruise wail out "Pour Some Sugar On Me" and not want to die a little bit—but you cannot say he doesn't devote himself to the part. For all his undeniably creepy intensity and general craziness, Cruise never goes halfway and never mails it in: He gives you more than you were asking, more, probably, than any sane actor would or should. Watching him just go balls-out over-the-top—including a bravura, oddly hypnotic, holy-shit-is-he-really-doing-this rendition of "Wanted Dead Or Alive" that has more sincerity in it than Jon Bon Jovi has expressed in 20 years—is, in a batshit way, sort of inspiring; Cruise just fucking goes for broke. It's not necessarily good, but it's insanely watchable, and every scene he's not in, you keep waiting for him to come back. (Fortunately, Shankman obliges, basically ceding the whole second half of the film to Cruise.) It's impossible not to admire him for it. And that probably tells you all you need to know about Rock of Ages: Tom Cruise is the best, and probably most metal, part of it. Rating: 8.

Grierson & Leitch is a regular column about the movies. Follow us on Twitter, @griersonleitch.