the best acting...

Hootsmon

role/performance by a woman is.....

and by a man.......

BigBearKris

DeNiro in "Raging Bull" and "Godfather II".

Meryl Streep in "Kramer vs Kramer" & "Sophie's choice".

munckee

My favourite is Paul Newman in cool hand Luke. Probably the best is jack Nicholson in as good as it gets. 

Sassafras

Antony Hopkins in pretty much everything he's in. Natural, restrained and subtle. Always believable.
Joanna Page in Gavin & Stacey simply because of her brilliant smile. It's infectious.
Toni Collete's pretty convincing too.
Worst, most hammy exaggerated actor: Al Pacino.

axisus

That's a tough question. There's something to be said for underplayed performances, and a particularly good one is good old Pete Postlethwaite in Brassed off. I wouldn't like to call anything best though.

Alvin

Lassie in Lassie Come  Home.

ourmaninthenorth

Jane Fonda - Klute.

George Clooney in "Oh brother where art thou.." 

Dominic

Alan Rickman in anything

Lodious

My favourite performance a woman (or man) is Vicky McClure in This is England where she visits the doctor. So powerful and totally believable.

Best role for a man, James Gandolfini in the Sopranos or Robert Di Niro in Taxi Driver. 

Best role for a woman,Audrey Tautou in Amelie. Margot Robbie was pretty good in I, Tonya too

ICBM

Juliette Binoche in The English Patient.

Colin Firth in A Single Man.

BigBearKris

Jack Nicholson in "Chinatown".

Shrews

Daniel Day Lewis as Bill the Butcher in Gangs of New York

Charlize Theron as serial killer Aileen Wuornos  in Monster (based on a true story)

The beautiful face of Dior was simply incredible (and unrecognisable) in her lead role that won an Academy Award

Charlize for Dior



Charlize in Monster

Phil_aka_Pip

by a man: Ian Lavender as Pte Pike in the Dad's Army episode where they dressed up as German soldiers to make a war training film

by a woman: couldn't tell you

Bygone_Tones

anyone in a toothpaste advert

scrumhalf

Spencer Tracey in pretty much anythg you care to mention.

stimpsonslostson

Not necessarily “best” but very memorable,

Gary Oldman- Leon

Frances McDormand- Almost Famous

Best-Chiwetel_Ejiofor in 12 years... his whole performance was breathtaking. 

blobb

Alec Guiness in Kind hearts and Coronets.

BigBearKris

Daniel Day-Lewis in "There will be blood" is also worth a mention.

Bellycaster

Theresa May & Jean-Claude Juncker..............in...............................Brexit!

At Cinemas near you from Friday!

*Runs Away*

  

Alvin

Aksel Hennie , Headhunters .

Bellycaster

OK, my 2nd serious answer:

Malcolm McDowell in "A Clockwork Orange"


Also special mentions to Jack Nicholson in "The Shining" and Joe Pesci in "Anything Where I Play a Little Sadistic Bastard"