Here are some actors and what I consider their top 5 best performances(Be it Main actor or Supporting) I can't wait to read your replies and choices-:)

Harrison Ford

1)The Mosquito Coast
2)Witness
3)Frantic
4)Star Wars
5)Raiders of the Lost Ark

Clint Eastwood

1)In The Line of Fire
2)Unforgiven
3)Million Dollar Baby
4)Dirty Harry
5)The Outlaw Josey Whales

Ed Harris

1)Pollock
2)Jackknife
3)The Human Stain
4)GlenGarry GlenRoss
5)Gone Baby Gone

Tommy Lee Jones

1)In The Valley of Elah
2)JFK
3)Cobb
4)The Fugitive
5)Natural Born Killers

Robert DeNiro

1)Godfather II
2)Raging Bull
3)Taxi Driver
4)Midnight Run
5)Casino

Al Pacino

1)Godfather II
2)Scarface
3)Serpico
4)Dog Day Afternoon
5)Scent of a Woman

Gene Hackman

1)The Conversation
2)The French Connection
3)Unforgiven
4)The Royal Tenenbaums
5)Superman

Dustin Hoffman

1)Midnight Cowboy
2)Kramer vs. Kramer
3)Lenny
4)Tootsie
5)Rain Man

Robin Williams

1)Good Will Hunting
2)Good Morning Vietnam
3)Dead Again
4)Awakenings
5)The Final Cut

George C. Scott

1)Patton
2)Doctor Strangelove
3)The Changeling
4)Fire Starter
5)Exorcist III

Gregory Peck

1)To Kill a Mockingbird
2)MacArthur
3)The Omen
4)Cape Fear(The Original)
5)Other People's Money

Paul Newman

1)The Verdict
2)Cool Hand Luke
3)The Sting
4)Road to Perdition
5)Nobody's Fool

Bruce Willis

1)12 Monkeys
2)The Sixth Sense
3)Die Hard
4)Unbreakable
5)Hostage

Anthony Hopkins

1)The Remains of the Day
2)The Silence of the Lambs
3)Shadowlands
4)Audrey Rose
5)The World's Fastest Indian

Sean Penn

1)Mystic River
2)Dead Man Walking
3)Sweet and Low Down
4)Casualties of War
5)Fast Times at Ridgement High

Michael Douglas

1)Traffic
2)Wonder Boys
3)The American President
4)Wall Street
5)Romancing the Stone

Tim Robbins

1)The Shawshank Redemption
2)The Mystic River
3)The Player
4)Bull Durham
5)Cadillac Man

Morgan Freeman

1)The Shawshank Redemption
2)Million Dollar Baby
3)Driving Miss Daisy
4)Nurse Betty
5)Glory

While I certainly haven't seen most of the films these actors made, I would add Dead Poets Society to Robin Williams' list and Fatal Attraction to Michael Douglas'.

Dead Poets Society is a good addition for Robin Williams-:)

I was suprised to You didnt have goodfellas in for De Niro and i thought Dustin Hoffman in Meet the Fockers wasa a great movie and he played the part so well

I would have put Goodfellas in for De Niro as well.Ive not seen midnight run so can't comment on it..

My five best, not in order:

Marlon Brando in "Streetcar Named Desire"
Robert DeNiro in "Raging Bull"
Robert Duvall in "True Confessions"
Meryl Streep in "Angels in America"
Helen Mirren in "The Queen"

Duvall was in True Confessions?

Robert Duvall
1. Godfather
2. Lonesome Dove
3. Open Range
4. Broken Trail

a1, you really missed out on Paul Newman. Here's my list and a few others (in no particular order):

Paul Newman
1. Cat on a Hot Tin Roof
2. The Hustler
3. Hud
4. Cool Hand Luke
5. The Long Hot Summer

George C. Scott
1. Patton
2. Dr. Strangelove
3. The Hustler
4. The List of Adrian Messenger
5. The Flim-Flam Man

John Wayne
1. Stagecoach
2. The Searchers
3. The Man Who Shot Liberty Valance
4. The Quiet Man
5. She Wore a Yellow Ribbon

Michael Douglas
1. Wall Street
2. Falling Down
3. Fatal Attraction
4. The War of the Roses
5. The China Syndrome

Harrison Ford
1. The Fugitive
2. Witness
3. Star Wars
4. Raiders of the Lost Ark
5. Patriot Games

Frank Sinatra
1. Some Came Running
2. The Joker is Wild
3. The Man With the Golden Arm
4. From Here to Eternity
5. A Hole in the Head

Marlon Brando
1. The Godfather
2. On the Waterfront
3. A Streetcar Named Desire
4. The Wild One
5. Apocalypse Now

Adding four more (again, in no particular order):

James Stewart
1. Mr. Smith Goes to Washington
2. Its a Wonderful Life (sorry, Mick)
3. Rear Window
4. Shenandoah
5. The Man Who Shot Liberty Valance

Humphrey Bogart
1. Casablanca
2. Dead End
3. The Maltese Falcon
4. The African Queen
5. The Caine Mutiny

James Cagney
1. Yankee Doodle Dandy
2. White Heat
3. Angels With Dirty Faces
4. The Public Enemy
5. Mister Roberts

Gary Cooper
1. Meet John Doe
2. Sergeant York
3. High Noon
4. The Pride of the Yankees
5. The Court Martial of Billy Mitchell

Stewart's the saving grace of It's a Wonderful Life. But for him, it's a piece of unadulterated filth.

Ed Harris

1) State Of Grace
2) Pollock
3) Jacknife
4) Empire Falls
5) Glengarry Glen Ross

Robert De Niro

1) Raging Bull
2) The Deer Hunter
3) The King Of Comedy
4) The Godfather Part 2
5) Taxi Driver

Al Pacino

1) The Godfather Part 2
2) The Godfather
3) Dog Day Afternoon
4) Scarecrow
5) Donnie Brasco
Honorable Mention - Panic In Needle Park

Gene Hackman

1) The Conversation
2) Scarecrow
3) The French Connection
4) Superman
5) The Royal Tenenbaums

Dustin Hoffman

1) Straight Time
2) Straw Dogs
3) Midnight Cowboy
4) The Graduate
5) Marathon Man

Marlon Brando

1) A Streetcar Named Desire
2) Last Tango In Paris
3) On The Waterfront
4) Reflections In A Golden Eye
5) The Godfather

Charlotte Rampling

1) The Night Porter
2) Under The Sand
3) The Verdict
4) Stardust Memories
5) Swimming Pool

Meryl Streep

1) Sophie's Choice
2) The French Lieutenant's Woman
3) Kramer vs. Kramer
4) Angels In America
5) One True Thing

Disappointing absences: For De Niro, Mean Streets, The Deer Hunter; for Hoffmann, All the President's Men; for Hackman, Mississippi Burning, Night Moves; for Stewart, Vertigo (one of the most convincing portraits of tormented masculine obsession ever, for me).

Paul Newman
1. Somebody Up There Likes Me2. Cat on a Hot Tin Roof
3. Cool Hand Luke
4. The Long Hot Summer
5. The Sting

Michael Douglas
1. Wall Street
2. Falling Down
3. The Ghost And The Darkness
4. Fatal Attraction
5. The China Syndrome

Harrison Ford
1. Raiders Of The Lost Ark
2. Witness
3. Star Wars
4. Regarding Henry
5. Patriot Games

Frank Sinatra
1. The Man With the Golden Arm
2. The Joker is Wild
3. From Here to Eternity
4. Guys and Dolls
5. A Hole in the Head

Marlon Brando
1. On the Waterfront
2. The Godfather
3. The Wild One
4. A Streetcar Named Desire
5. Sayonara

James Stewart
1. Mr. Smith Goes to Washington
2. Rear Window
3. Vertigo
4. Glenn Miller Story
5. The Stratton Story

Humphrey Bogart
1. Casablanca
2. The African Queen
3. Dead End
4. The Maltese Falcon
5. The Caine Mutiny

James Cagney
1. White Heat
2. Yankee Doodle Dandy
3. Angels With Dirty Faces
4. Mister Roberts
5. City for Conquest

Robert DeNiro
1. Raging Bull
2. Godfather II
3. Cape Fear
4. Goodfellas
5. Taxi Driver

Al Pacino
1. Godfather II
2. Scent of a Woman
3. Scarface
4. Serpico
5. Dog Day Afternoon

Dustin Hoffman
1. Rain man
2. Papillon
3. Midnight Cowboy
4. The Graduate
5. Tootsie

Jack Nicholson
1. One Flew Over The Cuckoos Nest
2. The Shining
3. The Last Detail
4. Easy Rider
5. Prizzi's Honor

"Msr. Spellacy's table..."

Headwaiter: I thought that Msgr. Spellacy would be dining with Mr. Amsterdam.
Tom Spellacy: Well, you thought wrong, fuckhead.

It was his favorite film of all the movies he made (as well as mine).

It's been great reading this stuff-You guys all brought to light great performances-I cant believe I didn't mention Ed Harris in EMPIRE FALLS-Loved it! DeNiro could also be mentioned for Awakenings.

Jimmy Stewart

It's A wonderful Life
Rear Window
The Philadelphia Story
The Man Who Shot Liberty Valance
MR.Smith Goes To Washington.

Humphrey Bogart

The Caine Mutiny
Casablanca
The Treasure of the Sierra Madre
The Maltese Falcon
The African Queen

Robert Duvall

Tender Mercies
The Apostle
Lonesome Dove
Open Range
The Paper

Kevin Costner

Mr. Brooks
Open Range
Bull Durham
Field of Dreams
Silverado

Meryl Streep

The Bridges of Madison County
Angels in America
Out of Africa
Ironweed
Kramer vs. Kramer

Jack Nicholson

A Few Good Men
One Flew Over The Cuckoo's Nest
Chinatown
The Pledge
About Schmidt

Sir Lawrence Olivier

1. Hamlet
2. Spartacus
3. The Boys From Brazil
4. The Jazz Singer
5. Richard III


Katherine Hepburn

1. Guess Who's Coming To Dinner
2. The African Queen
3. On Golden Pond
4. The Rainmaker
5. Adam's Rib


Spencer Tracy

1. Inherit The Wind
2. Guess Who's Coming To Dinner
3. Boy's Town
4. The Old Man and The Sea
5. Edison The Man

My Updated Gene Hackman. Thanks to Capo for reminding me of Night Moves. I knew my list wasn't right while looking at it.

1) The Conversation
2) Scarecrow
3) Night Moves
4) The French Connection
5) Superman


Jimmy Stewart

1) The Man From Laramie
2) Vertigo
3) The Shop Around The Corner
4) Destry Rides Again
5) The Naked Spur


Humphrey Bogart

1) In A Lonely Place
2) The Big Sleep
3) The Maltese Falcon
4) They Drive By Night
5) Casablanca

Robert Duvall

1) Lonesome Dove
2) Tender Mercies
3) The Apostle
4) The Godfather
5) The Godfather Part 2

Jack Nicholson

1) The King Of Marvin Gardens
2) The Last Detail
3) The Passenger
4) One Flew Over The Cuckoo's Nest
5) About Schmidt

Barbara Stanwyck

1) Double Indemnity
2) The Lady Eve
3) Ball Of Fire
4) Forty Guns
5) Baby Face

Katharine Hepburn

1) Bringing Up Baby
2) Love Affair
3) The Philadelphia Story
4) Long Day's Journey Into Night
5) Adam's Rib

Cary Grant

1) Notorious
2) Bringing Up Baby
3) Only Angels Have Wings
4) North By Northwest
5) His Girl Friday

Laura Linney

1) You Can Count On Me
2) The House Of Mirth
3) The Savages
4) The Squid And The Whale
5) Kinsey

Jeffrey Wright

1) Angels In America
2) Basquiat
3) Broken Flowers
4) Boycott
5) Syriana

For Robert Duvall I would add The Great Santini.

Lt. Spellacy (Duvall): You remember Dominic LoPresti, that little greaseball who tried to muscle in on Jack Amsterdam's construction business? So Jack takes him down to a laundry in Lincoln Heights, stuffs him into a dryer--shrinks the poor bastard down to 40 lbs.
Msgr. Spellacy (DeNiro): Is that a fact?
Lt. Spellacy: Des, I don't know the Holy Ghost for a fact. But you're in the Holy Ghost business, so I believe you...
Msgr. Spellacy: ...meaning I should believe you?
Lt. Spellacy: No...if you want to step in s**t and think it's clover, then don't believe me."

DeNiro in Raging Bull was one heck of an authentic portrayal.