Working within the assumed limits on this "All Time" list, i.e. ignoring theater and TV, restricting myself to the last 30 years or so, and in no particular order (but including actresses)...
- John Hurt
Remember Chancellor Sutler in V for Vendetta? Hurt played him, and also his *exact counterpoint* in 1984 superbly. Need I mention the chest burster?
- Jim Broadbent
As a character actor, he's that guy who's been in everything but you can never remember his name. This is a tribute to how well he plays the role, rather than playing himself.
- Brad Pitt
Can play the handsome, generic lead male in any piece of Hollywood fluff, but can range into convincingly deranged (12 monkeys, Fight Club). Remember the boxing gypsy in Snatch? He also perfectly sends up some of his own vacuous roles in Burn After Reading.
- Cate Blanchett
Manages an excellent range of roles and films, despite the appalling lack of such opportunities. From shy and withdrawn in Sense & Sensibility to supreme authority in Elizabeth and in the Lord of the Rings films.
Also excellent in Veronica Guerin.
- Sigourney Weaver
Sure, I'm an Alien fanboy, but can you think of any other woman in the lead role of an action film who can actually put some depth into the character?
EDIT: I feel bad about not mentioning Meryl Streep, but shamefully I've never seen a film with her in.