Olivia Colman was an easy pick for me but I don't want to discredit in any regards the excellent work of Melissa McCarthy in Can You Ever Forgive?. Definitely the only two ladies on the ballot that are award & nomination worthy.
Glenn Close may have been the best thing about her film but at best that is a back handed compliment. If any moment rubbed me up the wrong way in 2018 it was her response to the King of Sweden (or Norway?) "I'm a kingmaker" when he asks her what she does. Urgh. Proof that even an actress of the calibre of Close can't save clunky material.
Whilst I loathed A Star is Born, Lady Gaga was the one redeeming presence in the film for me. She really didn't have a great deal to do and was completely inoffensive and with a very pleasant screen presence but had no place earning awards or nominations for her performance.
As for Yalitza Aparicio, well it really wasn't a performance - she simply appeared in the film. Its clearly what Cuaron wanted but aside from running into the water and then all of them having a group hug she barely registered.
Emma Stone & Rachel Weisz belonged in this category and I'd like to think that if Fox had done the right thing a campaigned for all three Favourite leading ladies, that they may have made history and all got nominated - but we'll never know.
There were lots a great performances by actresses in leading roles aside from Colman, McCarthy, Stone & Weisz, though some of them won't be eligible until 2019 and are bound to get overlooked:
Tao Zhao, Ash is Purest White in the best role yet that her husband has written and directed for her to date in the most interesting collaboration of director/actress in China since the Gong Li/Yimou Zhou days. The film may fall apart in the last act by Zhao's performance does not;
Halldora Geirharosdottir, Woman at War playing an environmentalists warrior with material yearnings (to be remade by and starring Jodie Foster - pass me a sick bag please);
Melanie Thierry, Memoir of War as the legendary Marguerite Duras during the dying days of WW2 that provides Thierry with one particular scene that most actresses can only dream of;
Marie Baumer, 3 Days in Quiberon as the legendary Romy Schneider in shocking decline that was almost a preface for her untimely death a short time later;
Ana Brun, The Heiresses a newcomer to cinema who I understand gives her film debut performance as woman a timid, sheltered woman forced into her own being and new life experiences with such beautiful understatement;
Kathryn Hahn, Private Life given probably her best role to date that she seizes with pathos and humanity. I've been a fan for a while now and I hope we see prominent roles in the future;
Lea Drucker, Custody I don't think I've ever seen a film or performance tackle a divorcee with the intensity of this. Drucker get puts through the wringer and she's up for everything that director throws at her. 2018 French realism at its best - at least she has a Caesar
;
Ioana Jacob, I Do Not Care If We Go Down in History as Barbarians as a woman preparing to put on a public show with details the horrors of a particular event from WW2 in Romania who in turn discovers some unpleasant hard truths about the world we live in today;
Kiki Layne, If Beale Street Could Talk full of passion and quiet determination. It wasn't until I have spoken to friends in recent weeks why this film didn't fare to well with the Academy and general audiences - responses have been heavily muted but I was transfixed and Layne's performance so deserving of a nomination over some of what did eventuate;
Maripier Morin, The Fall of the American Empire playing a tart (and a very well paid one) with a heart and a brain and she is gorgeous to boot;
Angourie Rice, Ladies in Black as a young woman in dreary Australia in the late 1950's beginning interested to all sorts of foreign delights with eyes wide open.