I've been thinking about this for a while and I'm torn. There are problems with it. Take De Niro, for example. Based on his filmography alone he should be near the top of the list. There's no doubt he has been in some great films, Heat, Casino, Taxi Driver and the Godfather to name a few. But does that make him a great actor? I'm not so sure.
Kevin Spacey, Edward Norton, and Gary Oldman are high on my list