There's a reason Bloom became a breakout star and insta-heartthrob as a supporting player in two of the last decade's biggest trilogies: He's only good in small doses, or really just as a smirking, swashbuckling sidekick. But watch him lead a movie? You'll be as suicidal as his agonizingly insipid character in the equally laborious Elizabethtown. Bloom's range is too limited, his delivery too catatonic, and he doesn't have an iota of gravitas to pull off a Gladiator wannabe like Kingdom of Heaven. Pretty boy looks can't hide the cipher underneath forever. Notable Exception: The Lord of the Rings trilogy

The best two words to describe Blucas are "just there," because that's what he is. He's handsome, not doubt about it, but his characters always tend to only exist to advance the plot or develop other characters around him. Even Buffy's vampire boyfriends had more life than Riley, her unremarkable human beau. To put it simply: Blucas is just an average Joe, which is fine in real life, but rather unremarkable onscreen. Notable Exception: Necessary Roughness

Bosworth has two different colored eyes, which is about the most interesting thing you can say about her. If you want the cookie-cutter blonde in a nutshell, look no further than her horribly miscast role as Lois Lane in Superman Returns: boring, deadening, forgettable and more bland than a gluten-free diet. Be happy that she and wet blanket ex-beau Orlando Bloom have never shared the screen together. Notable Exception: She's sufficiently adequate in the ensemble heist drama 21.

Whether playing an ass-kicking former CIA agent on Person of Interest or a homeless drug addict in Pay It Forward, Caviezel brings the same blank, emotionless gaze to all of his performances. Even when his characters are cracking jokes or running for their life, Caviezel seems like he's just seconds from falling asleep. Somebody get this guy some coffee! Notable Exception: The Passion of the Christ

Blame Jar Jar Binks all you want, but the real killer of the Star Wars franchise was the ever-hollow Christensen. Despite multiple attempts by Hollywood to make him a star (see also: Awake, Jumper) his wooden line readings and complete lack of personality always derail his efforts. Maybe that's why Darth Vader truly wears a mask. Notable Exception: Shattered Glass

It's easy to just focus on Crawford's beyond-blue eyes and forget your better judgment, but we all know the truth: He's boring. Even Gossip Girl's over-the-top drama couldn't seem to make Crawford exciting. No matter who he's acting with, Crawford always falls flat — particularly when opposite Leighton Meester, whose headbands were always far more interesting than the actor's expressionless (albeit beautiful) stare. Notable Exception: Twelve

Thanks to his pretty boy looks, Hartnett made a name for himself in both acclaimed fare like The Virgin Suicides and Black Hawk Down and popcorn blockbusters such as Pearl Harbor. However, the actor's monotone voice and vacant stare left much to be desired in the personality department. Even worse, Harnett's seeming indifference to Hollywood makes it a big head-scratcher as to why he ever wanted to be an actor in the first place. Notable Exception: Penny Dreadful

Despite having the looks and gossip-blog appeal to be one of Hollywood's finest starlets, Heard hasn't been able to truly break through. Perhaps that's because she's all sizzle and no steak. Heard basically sleepwalks through any of the roles that require her to do more than take her clothes off, which was certainly a problem on NBC's decidedly un-sexy Playboy Club. Given her lively appearances on talk shows, we know she can do better; we're just waiting to see it. Notable Exception: Pineapple Express

From her days on Dawson's Creek to big screen fare like Batman Begins, Holmes has practically played the same mindless, unemotional character again and again thanks to her limited range. (Chris Nolan didn't even want to bring her back to kill off her character in The Dark Knight!) Dawson could die, and she'd still be dead behind her eyes. Notable Exception: Pieces of April

Kelly is usually deployed as eye candy, which works fine enough when she's in a large ensemble on such shows as Friday Night Lights or Parenthood. But asking more of her — including stepping into the high heels of such an iconic franchise as Charlie's Angels — and the cracks become obvious. Her actions and line readings are vacant and non-believable. In other words, we had trouble telling her apart from the robots surrounding her on Almost Human. Not a good sign. Notable Exception: Parenthood

Though Lively wasn't the worst part of Gossip Girl, a character who seems to be the hottest thing in New York should at least have some, we don't know, feelings? Instead, Lively has the same slow drawl that makes her seem like she's high — which worked for her in Savages, even though she was far from superb in that film as well. Notable Exception: The Town

Usually a Southern twang helps lend a bit of charm, but for the former model-turned-actress, it only serves to remind us that MacDowell isn't really much of a chameleon when it comes to her acting. In fact, in Greystoke, Glenn Close had to dub MacDowell's voice because her Southern accent was too pronounced to play a convincing Englishwoman. It's clear that her beauty helped her land many of her leading roles — Green Card, Groundhog Day and Four Weddings and a Funeral among them — but it was always her male lead that had to bring the personality. Notable Exception:Sex, Lies & Videotape

Let's be honest: Can anyone besides Jude Law really pick Sienna Miller out of a lineup? More known for the men she dates than the roles she plays on screen, Miller has been a tabloid fixture but has never been able to cross the line into being a box office draw. Perhaps she should stick to modeling? Notable Exception: HBO's The Girl

O'Donnell had us fooled when he was mixing it up with Al Pacino and Matt Damon. But slap this guy in a superhero suit and his flaws instantly become apparent. His emotional range stretches from boyish dumbstruck glee to slightly-furrowed-brow anger, and all the stops along that narrow spectrum almost always read cheesy. Amazingly, rubber nipples weren't the worst part of Batman & Robin. Notable Exception: Circle of Friends

Never before has a mildly emphatic "Whoa," carried an actor so far. The good-looking leading man never had to emote much as long as the action or story was sexy enough. Who needs complicated acting when there are reflective sunglasses, 360-degree mind-blowing effects and logical paradoxes to dazzle you? As the plots and visuals get more and more convoluted (Constantine, A Scanner Darkly), one can always count on good ol' Keanu to bring the grounding force of bland mundanity. Notable Exception: Bill & Ted's Excellent Adventure. (Or even better, the sequel, in which he plays a very convincing robot!)

Bella Swan doesn’t start out as a vampire in the Twilight series, but you'd never know it from Kristen Stewart's dead eyes. After exploding onto the scene as the heroine of the teen trilogy, Stewart's consistent "I'd rather be anywhere but here" off-screen demeanor made viewers wonder why exactly she had two guys fighting over her in the first place. Notable Exception: The Runaways

Movie studios keep trying to make Sam Worthington happen. Despite starring in the single biggest film of all time (Avatar) and other action films like Terminator: Salvation and Clash of the Titans, he's still not a household name. Why? Because he doesn't stand out in any way shape or form from the many muscled-up action stars that came before, and the many that will come after. In an age where superheroes like Iron Man and Spider-man can save the world and get a few laughs, Worthington's blandness can't save his impressive, but generic, good looks. Notable Exception: Avatar (Take a bow, Zoe Saldana!)