I remember watching a documentary that explored how Steve McQueen became the superstar that he was. Performing amongst some of the best ensamble casts ever grouped together (The Magnificent Seven, The Great Escape), McQueen was constantly active, even in the shots where he was in the background. He'd be playing with his hat or moving his arms in a certain way that would subtlely distract the audience from the other actors in the shot and bring the attention to himself. While Ferrell doesn't have an ensamble to compete against, it would seem that he has some work to do to convince people he's still an actor worth paying for.
One of the things I noticed most about In Bruges (which is in Belgium, by the way) was Colin Ferrell's face. Whether it's shot from far away or in a close-up, Ferrell's face is so expressive. It's noticeable but not distracting. I would argue that his role as Ray is the most emotionally developed character of Farrell's career. Don't get it twisted, I sorta understood the motivation behind Bullseye. He liked darts, right? His expressions in In Bruges really help flesh out his character. They may seem silly in stills but in the right context, they work.