Last 60 years, people. No Cary Grant or Jimmy Stew or any of the usual suspects of the Golden age.
This is just my opinion, of course. Acting and all things to do with movies are 100% subjective.
5- Robert DeNiro- Raging Bull-
One of the best transformational performances you will ever see. DeNiro embodies the character he plays to a tee and his ferocity and screen presence are unrelenting.
4- Heath Ledger- The Dark Knight-
Quite possibly the most singularly iconic performance by any actor in cinema history. Ledger immerses himself into his role by completely changing his voice, his laugh, his body language/ mannerisms, and even his facial expressions. He turns an otherwise cartoonish character into a force of nature.
3- Dustin Hoffman- Tootsie-
Funny, charming, and charismatic all wrapped up into one. The sight of Dustin Hoffman prancing around dressed as a woman still causes me nightmares to this day.
2- Daniel Day Lewis- My Left Foot-
Never before has an actor so thoroughly portrayed someone who suffers from a mental or physical disability. There is so much room for error when playing a character like the one DDL played, and yet Mr. Lewis “nails” the part.
1- Heath Ledger- Brokeback Mountain-
Very rarely do you see a young actor give a performance with so much going on underneath the surface. Mr. Ledger does a fantastic job balancing emotional outbursts (Why don’t you just let me be, huh?”) with inner emotional conflict. One of the few examples of a truly flawless performance.