What's the difference between a good and great actor?

Take a look at someone like Leonardo Dicaprio. From his early work to what he is doing now, there is a huge difference.
A lot of it has to do with the rolls the actors get, aswell.

Most people on TV these days aren't expected to act naturally. They act like people on TV act, if you know what I mean.

For instance, watch TV with the sound off for half an hour (listening to people's words distract from body language). You'll see at least one person shaking their head from side to side as they talk. Quick means angry. Slow means they're trying to same something fascinatingly insightful. So many people do it on TV, but who does this in real life? Certainly no-one I know.

Great actors are people who don't "act". They inhabit their characters and become them. Like you say, though, it's not always easy to pick out how far up the scale someone is.

I don't know how to act, but I can see the differences between actors.

The most important thing is: is the actor convincing? If the character is supposed to be furious, but the actor makes it look like he's just annoyed... Then that is bad acting and a bad actor.

A good actor can make any character feel "real", so that the audience isn't just watching a celebrity shooting people, but more like a cop doing his job (just an example).

A good actor can entertain you. A great actor will engage you and convince you of their role.

Look at Mel Gibson in "Conspiracy Theory", or Johnny Depp in "Fear and Loathing in Las Vegas". They really transform themselves, becoming other people. All the subtleties. Most actors aren't capable of that, and that's a shame...

a good actor engages the audience and makes you empathize with them. they also make you believe they ARE the character they're playing. a GREAT actor does all those things but moves you to tears or goosebumps or elicits any emotional/physiological response. Edward Norton, in my opinion, is one of the best actors out there. his performance in Primal Fear was brilliant, almost as much so as his performance in American History X.

And I kow that "The Return of the King," and the Lord of the Rings trilogy in general is fantasy and yet has good acting.

I know that Alfred Hitchcock popularized the thriller among the upper middle class, and yet he had famous actors like James Stewart.

Never said there aren't exceptions. Mostly I just want to emphasize that a good actor is not necesarily someone who makes something feel real.

Completely agree with most of you. A good actor makes the movie/show/performance seem real and true... in REALLY general terms. Sometimes a good actor is good at making things seem really UNreal.

For example, consider the genre of comedy, or the highly stylized "comic book," styles of film making. Whether in "Anchorman," "The Office," or even "The Daily Show," Steve Carell is EXCELENT at portraying someone so dumb/delusional/eccentric, that an audience can't possibly believe anyone like that could exist.

Take Gerard Butler in "300." Every movement he makes, every pose he strikes, every word he speaks is SO overly stylized... even his costume is! (The Spartans wouldn't have left their chests, stomachs, and backs uncovered.) And yet, his overacting makes that film awesome.

I think dramatic actors get a better rep because audiences today go see "Paul" for a laugh or a date movie, but then bring up "The Departed" at more elegant things like dinner parties. Realism is percieved as sophisticated, whereas other genres like comedy, fantasy, and thriller are somewhat lower forms of entertainment, and therefore, the dramatic actors are thought to be superior, or "good." Don't get me wrong, Dicaprio and Damon were awesome in "The Departed," (and it's currently my favorite contemporary film), but don't mistake realism as the only measurement of good acting.

A great actor isn't acting. A good actor is.

In my mind Al Pacino (Scar Face) is by far the best actor of our time as he ceases to be Al and takes on the life, views, and even minuscule reactions of his character. It's insanity and utterly sublime but he truly forgets himself in his role.

There's also something akin to charisma in Al. I can't explain it but Brad Pitt has it as well.

It depends what you mean by a good Actor do you mean acting in entertainment or lying. In the entertainment part I think a good actor is someone who can play complete different characters and make them look completely different from the other characters they played in the past. I think a good liar is someone who is too perfect or someone that can play on emotions.

Ehh...ones better than the other?