What defines a good movie? It’s an important question with Rock of Ages, a film that manages to be uneven in its performances, messy in presentation, overly-gooey in its message and still shockingly, perversely entertaining.

Director Adam Shankman’s adaptation about a very particular time in rock history is as much a facade as the material it’s aping – which is to say that the falsities that were apparent in 1987 rock are exacerbated here. Those with an affinity for the days of Poison, the Crüe, and Bon Jovi are going to view Rock of Ages as something of an affront in its butchering of beloved pop rock standards (see Ballads, Monster). But if you’re able to view it at face value, Ages is seriously great fun. It goes from terribly awkward to plain terrible and then, by the time Tom Cruise is belting “I Want to Know What Love Is” directly into Malin Ackerman’s ass as if it were the world’s most precious microphone, it approaches the sort of classic camp that is far too rare.

This is the kind of effort that high school theater geeks would assemble if said kids got hopped up on wine coolers and cranked Poison records on blast – it feels that disconnected from the source material. Still, I’m hesitant to put Ages in the same category as Glee or even the Hairspray musical (another Shankman joint, adapted from the Broadway play which itself was an adaptation of a 1988 John Waters classic). You really need to see Ages with an open mind and accept it on its own terms, free of any context its own recognizable music or predecessors might try and provide.

This happens in spades.

A painfully awkward start doesn’t do the film any favors. Our introduction to Julianne Hough’s Sherrie Christian, the protagonist with dreams of being a singer, is jarring and haphanded. A small-town girl bussing into 1987 Los Angeles, she covers Night Ranger’s “Sister Christian” as she stares at her dreams out the window. That feels gangly enough. But when she’s joined by other passengers, one of whom resembles (and probably sings like) the stuffiest college professor this side of your dad’s Cardigan sweaters – a square who knows his edges are razor sharp. It’s a bizarre introduction to one of rock’s seediest eras – but such is Rock of Ages.

Sherrie arrives to Sunset Strip only to be robbed as soon as she gets off the bus. She’s taken in by Drew (Diego Boneta), a bartender for The Bourbon Room – the Strip’s most raucous rock temple. The Bourbon Room’s in bad shape, their inability to pay property taxes (which, like the sweaters, are for squares) threatens to shut the joint down. Owner Dennis Dupree (Alec Baldwin) and bar manager Lonny Barnett (Russell Brand, surprisingly great here) take a chance on Sherrie – letting her wait tables so she can screw Drew and dance and sing to her heart’s content.

The Bourbon Room, and Rock of Ages by extension, has one ace-in-the-hole that could potentially save this rec center of extreme (the state of mind, not the band) once and for all: Drew’s idol Stacee Jaxx (Tom Cruise) is en route for one last show with his band Arsenal before launching his solo career. Will Stacee’s hard-partying, hard-ballading ways produce a rock show worthy enough to restore The Bourbon Room to its former glory?

Not really, but it'll all work out anyways.

So much happens in Rock of Ages‘ two hours that it’s easy to get lost in all of it. There’s Catherine Zeta-Jones as antagonist Patricia, the mayor’s (played to delicious sleaziness by Bryan Cranston) wife who’s leading the charge to “take back the Strip.” There’s Paul Giamatti as Stacee’s slithery, money-grubbing manager. Then there’s Malin Akerman as Constance Sack, writer for Rolling Stone. She’s incredible here, and you will absolutely beg the rock gods to bestow as much Sack as they’re willing to spare.

The musical numbers are at first spotty but improve. Julianne Hough, who is not an actress, is the most uneven of the lot. The aforementioned “Sister Christian” bit doesn’t ingratiate her character to the audience. But her take on Extreme’s “More Than Words” is terrific, and enough to pull a tear from your eye. She falters in between the song and dance spots, as there’s nothing going on behind those gorgeous baby-doll eyes. It’s fitting that this is an adaption of a Broadway musical, as it’s clearly where girl belongs.

It’s Tom Cruise’s Stacee Jaxx that people seeing Rock of Ages will want to talk about. His Dennis DeYoung-esque voice lends the film gravitas befitting of a true rockstar. He and Akerman take on Foreigner’s “I Want to Know What Love Is” with such shameless, reckless abandon that they deserve much of the credit for keeping the film afloat. It’s perverse, degrading and constitutionally sexual in all the finest ways. Ages straddles the line between prestigious Broadway adaptation and overt camp up to this point, but as Akerman strips and Cruise preens – the material is embraced for what it truly is: PG-13 raunch.

Odd to say that the film never truly dials in until making peace with going completely off the rails. But once it settles into this role, everything improves. Even the musical numbers, stiff and rigid in the beginning, become freer performances. Shankman and cinematography Bojan Bazelli shoot the action too closely in the beginning of the film, a product of small sets that don’t have the expanse of a theatrical stage. The later numbers improve as you get the sense everyone makes their own peace with the material.

It’s hard to criticize a film that wears its flaws on its frilly, neon sleeve the way Rock of Ages does. Its disingenuousness is befitting of an era in rock so false, so vapid, so artistically bankrupt that its one major contribution was ushering in the Grunge Era. These performers are too pretty to feel truly authentic – perhaps the point. Only Baldwin, in his weathered Baldwin way, wears the much earned badge of hard living on his face.

Baldwin’s singing is thankfully kept at a minimum, and his relationship with Brand in the film is where Ages finds its heart. Boneta and Hough greatly bungle their scenes together, but thankfully they’re not the only love story in the film. Let’s just say that the most intimate kiss in the film is not reserved for Boneta or Hough.

It’s certainly cheese, but sometimes cheese can be delicious (in addition to causing mild constipation). This is a film that’ll be enjoyed years from now – at midnight showings, amidst drunken patrons, lyrics and a bouncing ball dancing across the bottom of the screen. A camp film that’s great fun, Rock of Ages might be a different spectacle than you’re used to. But it’s absolutely a spectacle worth enjoying.

Out of a Possible 5 Stars

Follow Tim on Twitter: @roboTimKelly