Hollywood actors inhabit three tiers.
There are the true chameleons, who can assume any character or accent with ease and one can genuinely forget it's a performance. Joaquin Phoenix, for example.
The next rung belongs to the stars. At this level, viewers don't come to watch the character. They come to watch the actor, so beloved that the audience might even refer to the protagonist by the actor's name. Arnold, for example.
The final rung is my favorite. The actors on this level possess the power of the previous two tiers. They're wildly popular stars that can also contort their personality to resemble whoever they choose. Despite being beckoned to the theater by their star power, the audience is compelled by these actors' ability to disappear into a role. Whenever I think about this caliber of actor, I think of Javier Bardem.
In the video linked above, Vanity Fair and Javier Bardem give a retrospective of his career up to Dune. If you're a fan of Spanish cinema or an admirer of staggering talent, give the video a watch.