DANG IT, darn it, dang it, jn.
As I was going to sleep last night, I was talking to my wife about this topic and thought about Philip Seymour Hoffman and then remembered that I left him off my list of awesome actors earlier. I was so pissed off especially since we just saw "Charlie Wilson's War", in which he gave a performance that pretty much had Tom Hanks and Julia Roberts brushing his dust off their teeth. So I said that tomorrow morning I was going to get on here and remedy that huge omission. Of course I come into work this morning and the world was going to hell in a handbasket, so I couldn't get on until now, lunchtime. And you beat me to it, dangit. I think you have to start bandying Hoffman's name about when talking about today's short list of supreme actors.
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To touch on WOWs point about being a box office draw. That's why its a real conundrum of a question. You have to pursue the glitz, the glamour, and the notoriety to become a humongous personality, big enough to command screenwriters and producers to develop a movie whose entire goal is to act as your vehicle: Russell Crowe in Gladiator, Brad Pitt in Troy, Tom Cruise in Mission Impossible, etc. Once you have that personality, its almost impossible to completely immerse yourself in a role. Sure they'll go out there and do an indie flick, so call stretch their legs, but. . . And Derek is right about Marlon Brando, how he managed to do both is amazing and exceedingly rare. So what do you strive for as an actor? Fame or Brilliance?
As for what I think of Will Ferrell, eh, he's been Will Ferrell in most of his movies. In fairness, I haven't seen "Strange Fiction", yet, and people say he actually acted in that one.
Ed Norton is a very good actor. He does take movies off, though (e.g. The Score and Red Dragon)
Its awesome that your a Forrest Whitaker fan, you didn't mention it and it wasn't widely distributed so I'll assume you haven't watched it. GO SEE "The Last King of Scotland" RIGHT NOW!! Holy Mother of Pearl does Whitaker slam dunk a performance in that one.
The villain in Die Hard and the Harry Potter professor is Alan Rickman--a London Stage Theatre vet--always good for injecting a little pomp and arrogance into anything.
The guy in "Se7en" with Pitt is Morgan Freeman (how do you forget that one). Immensely likeable and a terrific screen presence but unfortunately has very little range. Tim Robbins is ridiculous good--I think he's a guy who might have sacrificed fame (box office draw) in pursuit of brilliance. Robin Williams, very very hit or miss.
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LakerFan. If you want to see Will Smith act his butt off, its not "Pursuit of Happyness" you're looking for. Its "Six Degrees of Separation", a film from 1993. Check it out if you haven't.
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Westkoast's point is spot on and happens all the time. M. Knight Shymalan practically begged Paul Giamatti (another good one to bring up, BTW, jn) to take the role in "Lady in the Water". Too bad Paul couldn't save an inherently flawed movie.