Some great choices.
Of course it is nearly impossible to find one best. I guess the question is a bit ironic, and the purpose is to get a list of some greats - as you did.
I also tend to like subtler actor's who don't really "perform" in any traditional sense. But my suggestion is in fact a performance. 
Great there are so many different techniques and ways of acting. If i recal Doillon's "Les doigts dans la tte", the actors were all unprofessionals but were stunning. Everything seemed real and unforced to me, and that is the greatest magic. If you forget the performer, his name, his reputation or personality, and start experiencing the character - of course that can also come from professionals, though i tend to think this only happens when they "depart" from themselves more than usually - or, imo in the case of Binoche and Bleu - identify themselves so much with the character that they don't have to play anymore (I think Bleu is as much "her" film as Kieslowski's). 
But it can also be nice observing a person on screen, regardless if he or she is acting effectively. For example I always enjoy watching Kevin Costner on screen, and usually he's just that - Kevin Costner.