With the exception of the Terminator movie he was in, everything I've seen Sam Worthington in has been terrible. Most notably Gash of the Tight Ones and Ham on a Lid. This dude is like the new Colin Farrell.
I also wonder how can Worthington be in so many movies, as if someone very powerful in Hollywood wanted him to be a huge star, whatever the price is... The question is : do people fall for this, I mean, does he have many fans ? I guess his looks and his "good guy" face make him a likable action hero for whoever doesn't mind bad acting. Because yes indeed, that guy can't act.
As for the movies he's been in, besides the decent Terminator salvation and, to some extent, The Debt (but the presence of Jessica Chastain made me very tolerant), I haven't seen him in good films either : Avatar has as much depth as his acting, the Titans are jokes for kids, Texas Killing Fields was one of the worst written films I've seen in ages, Last Night was a boring drama... I haven't watched Rogue. It looks fun.
However, as someone wrote above, I disagree totally with you when you write that he is "the new Colin Farrell". Farrell is not a brilliant actor (for example, he has recently shown his limits in Fright Nights), but still a decent one, and can be pretty good when he's well directed : In Bruges, Cassandra's Dream and the Malick are three examples that come to my mind. Anyway, in terms of charisma (I'm not even saying talent), Worthington and Farrell are like day and night.
Sam Worthington was pretty good in Aussie B-movies like Rogue, but I think that's about his limit. Credible talents like Elizabeth Banks must spit chips at having to play second fiddle to someone like Sam. But then, he's not exactly the only bad actor on display. Ed Harris is a bit sad - a good actor who made some great films, and now turns up in any old crap. I guess he thinks, if it's ok for Al and Bobby, it's ok for me. Then there's Ed Burns who was once, I think, a leading light but who now seems resigned to playing bit parts in B-movies. Jamie Bell isn't too bad, and of course there's Genesis Rodriguez. I'm not sure about her acting ability, since her contribution seemed to be limited to ensuring good shots of her very healthy looking chest. In fact, her breasts played such a prominent role they should have had acting credits of their own. Compared to most of the other acting on display they could have received Oscar nominations.
I agree he wasn't very good in this film, but then again this film was pretty crappy--weak script, direction.
My favourite film of Sam Worthington's is the Australian film, Somersault, also starring Abbie Cornish. He's wonderful in it, as is Cornish. It's a very heart-felt psychological story of two damaged people.
After seeing Worthington in it I thought for sure he was someone to watch. I liked him in The Debt as well, but otherwise he either chooses weak projects or is just stronger in Aussie films.