Dustin Hoffman - Rain Man
Bill Pullman - Independence Day, but only during his speech before the massive final assault.
Robert Deniro - Taxi Driver
Sylvester Stallone - Rocky
Jim Carrey - The Majestic
Jim Carrey - The Truman Show
Jim Carrey - Bruce Almighty
It's been so long since I've seen anything worth best performance. And I don't remember all the stuff I've seen long ago.
Here's a short list of fairly good performances.
Kevin Costner - Dances With Wolves
Michael Keaton - Batman and Batman Returns
IMO, Michael Keaton was the best Batman ever, when the series was dark and not so kid-centric.
Anyway, more when I feel like it. I mean when I come up with it.