Colin Farrell is incredibly good, considering he's nobody's idea of a bashful or sexually inexperienced man. (This is the guy who made a sex video of himself in which he pauses while eating his girlfriend out to say, "Holy fuck! My breakfast, lunch, and dinner right here, I'm not even fucking joking.") Farrell is an unpredictable little bullet of a star. In Minority Report (2002), he nakedly enjoyed stealing scenes from Tom Cruise, as if acting were a competitive sport played one-on-one and aerobically fast, like racquetball. And in Intermission (2003), his ferociously physical hooliganism — swinging a shovel as he ran from a crime scene through traffic — embodied a certain sociopathological allure that has been central to movies since forever. He seemed born for the medium, as much as James Cagney.
I can see why these supporting performances would have made directors think Farrell can do anything, but he can't. In Oliver Stone's Alexander (2004), Terrence Malick's The New World (2005), and Michael Mann's Miami Vice (2006), his limitations became stunningly clear. He lacks the breadth of personality to play an epic hero, even a flawed one. And apart from The Recruit (2003), in which the role of a filial apprentice justified his junior quality, his physical assurance isn't all-purpose enough for action heroes. Even his suits in Miami Vice seemed bigger than he did. (There's more than one set in the game of stardom; Tom Cruise retakes the lead.) When Farrell experiences doubt while playing a commander of men, he suddenly seems puny; the walls of those big-budget movies collapse inward on him.
On the positive side, it may be that Farrell's face is too particularly expressive for a generic knight in such overblown productions. His Alexander was embarrassing but no more so than Clark Gable's performance as Parnell. Farrell isn't dismissible, he's simply less adaptable than we might have expected. He's resourceful enough, however, that miscasting per se isn't the worst thing that can happen to him. In A Home at the End of the World (2004), he actually benefited from being miscast. His role as a gayboy's dream of a bisexual best friend — a pure-hearted stud who never says no and is never put out by his lovers' complexes and tantrums — was a pink smoke ring. Farrell obviously had to hold back to play that utterly innocent, blocked manchild, but the obviousness made him amusing to watch. The confusions that played on his face were so clearly crafted that I was drawn to the working actor even though I rejected the character he was playing. Something similar is going on in Ask the Dust, except that I don't reject the character.