What makes an actor/actress brilliant?

They get into the character and become the characters.

They are expressive even with only a glance or look.

I like actors who can engagingly convey complex emotions. From quiet and introspective to explosive or lively. I like a range.

A brilliant actor, in my opinion, is one that you aren’t quite sure what they’re really like. They play such a wide range of charactors so well, that you sometimes forget they are their own unique indiviual. Natalie Portman and Leonardo DiCaprio are like that for me.

A brilliant actor can step into any role and get lost in it, so that I don’t even notice who the actor is.
Look at Ed Norton Jr. playing the Illusionist and that scary kid in Primal Fear. He succeeded in transforming himself in those roles so thoroughly that he doesn’t even resemble the same person playing those roles.

What @marinelife said. I think if you have that down, you’re brilliant!

Charisma, and believability. The ability to evoke empathy.

As an actor, I can say it has something to do with physicality. Each character has a different walk, a different carriage. I work to find where in my body each character lives, and that knowledge informs the performance.

There is also knowing more than the mere plot. It’s knowing what happened before and what comes after the events of the play or the movie. In some cases, I’ve gone as far as writing a life story of the person I’m portraying.

Most modern actors leave me cold. There are a few performances I’ve seen that were heart-wrenchingly authentic. Colin Firth in The King’s Speech was one. It wasn’t simply his recreation of the stutter. It was his embodiment of character, the person. It was inspiring.

One often hears an actor talking about motivation in a scene, the “why” of the events. The actor has to know his/her objectives, both major and minor ones. A character’s desires are important. How an actor relays these to the audience must be nuanced and well thought out.

In my opinion, brilliant actors aren’t born. They’re trained. They study the craft of acting. They learn about their own foibles and face them unflinchingly and hopefully overcome them.

@Hawaii_Jake ; I couldn’t agree more. I have had a few acting successes when I had some really good personal experiences that helped me relate to the character. I thought I would pursue it and realized that I needed A LOT of training before I would have the ability to access a character quickly enough for a real live audition. Just living near LA would not be enough. (Lesson learned a few very embarrassing auditions later.)

@Hawaii_Jake What about the body motions while acting? As I act I can’t seem to find what to do with my body, hands and arms. I know in T.V. it’s not much of an issue, but for stage it is

@Earthflag : Motion comes from knowing where in your own body the character lives. Some characters are all in the head, and thus the body moves very little. Some are in the extremities, so the hands and feet are almost constantly moving.

If you’re having trouble knowing what to do with your body parts, that’s a symptom that more homework needs to be done. Study the character’s circumstances in the play, the objectives, the relationships to other characters, and obstacles. Translate those things into informed movement. Don’t simply walk across a stage to pick up an object. Know why that object is the most important thing for the character at that point in time. Do that, and your movement will have purpose.

A lot of it has to do with casting as well. If you take an excellent actor and place him in a role that is simply terrible.. he may do an outstanding job but it could still leave a bad aftertaste.

Incidentally, Paul Walker is one of the worst actors ever… just throwing that out there…

For me a performance is spectacular if I cannot see the performer, only the character. IMO an example was Ron Eldard performing Doubt on Broadway. He is my favorite actor of all time and watching the play I forgot it was even him. After the first scene, in which his character is saying mass, I literally crossed myself right there in the second row of the theater. That is a brilliant performance.

Whenever I watch television, I can almost immediately tell whether the people on it are acting or not acting. For example, t.v. shows like CIS and Operation Repo try to make things look “real life”, but I can tell there is “acting” going on there. On the other hand, when I watch the news, I can see that the people interviewed on news stories are “real people in real life situations.”

Really good actors and actresses are able to make it look like they’re not acting at all. But even the best actors and actresses still behave in a certain way that almost always looks scripted or acted. I can always sense it. Even films that are fictional but made to look like documentaries have people in it who are still over-acting the part.

I know of only one actress who made it look as though she wasn’t acting. That was a wonderful Japanese actress by the name of Hara Setsuko in the 1950s and early 1960s.

Screen presence, charisma & the ability to make work seem like it’s anything but.
Chris Walken has it, Martin Balsam had it & Robert Downey Jr shows promise.

My #1 test is: Do I honestly believe that a real person, in this situation in real life, would actually act exactly like this? Or do I feel like I’m watching a professional who is demonstrating how someone in that situation might act? If the former, then this person is a brilliant actor. If the latter, then no.

Like everyone has said it has as much to do with the physical expression through movement, walk, body language as it has to do with the delivery of the dialog. Here is a great clip where Meryl Streep talks a little about the process of making Bridges of Madison County. She talks about Clint Eastwood and her own acting process. I love the bit about the hand on the door. Now that is where you really see the non verbal expressiveness that makes a great actor.
http://www.youtube.com/watch?v=pul3Cp6aTEQ&feature=related

If they can make me fall in love with a character (or, to use another extreme) hate a character because of their actions and attitude (rather than because I find the actor to be lacking in the skills to portray that character in the way it probably should be) then I consider them to be a decent actor.

A favourite example of this is Charlize Theron in Monster. She portrayed a serial killer who, before I saw the film, I guessed I probably wouldn’t like very much or would be disturbed by her choices. In actual fact I felt so much compassion for this woman and truely felt that life dealt her a shitty hand that made her feel she had no other options than to commit the crimes she did. Theron managed to make me see beyond the murderer to a women that had been damaged by a cruel society. The scene where she tries to get a job and the person interviewing her treats her like absolute shit actually made me cry for her. The way her face dropped from an enthusiastic smile to that of disappointment and then anger made me want to punch the guy that had made her feel so worthless.

Skill in deceiving the viewer into thinking that the actor really is the character being portrayed