It takes a lot to make a movie great. There has to be excellent writing, production, direction, editing, and of course, acting. While the crew draws out the parameters for a movie, the actors are who color in the film to bring it to life, and without great acting, a great film can crumble.
These actors are the ones who deliver time and again, regardless of how good the script or the production of the film is. These are the greatest American actors who are alive today. Who are the best actors? That's up to you to decide. This list is votable and rerankable, and if you don't see someone on here that deserves a spot, feel free to add them, but make sure they're still alive.
http://www.ranker.com/list/best-living-american-actors/ranker-film,
Ben Foster
Brad Pitt
Dustin Hoffman
Ed Harris
Joseph Gordon-Levitt
Kevin Spacey
Paul Giamatti
Sean Penn
Tom Hanks
Viggo Mortensen