The_Lhc said:
Sorry but you can't include Leon in that list, she's brilliant in that.
Portman was perfectly fine in Leon, displaying as much emotional range as one might reasonably expect from a child actress. Unfortunately, her range didn't expand thereafter.
I'll also acknowledge that she went to great pains learning ballet for her role in Black Swan. (Not that I'm qualified to comment.) Portman is also very pretty, which helps account for her success.
Unfortunately, Portman is emotionally inarticulate. This lack of emotional insight works well during the first half of Black Swan, when she's playing a debilitatingly repressed character. However, Portman's lack of range is exposed during the transformation scenes, when she's required to shed all inhibition.
Several critics were fooled by Stallone's "performance" in Rocky. He was compared with Brando, De Niro, and Pacino. Vincent Canby was on the money when he described Stallone's performance as "an unconvincing actor imitating a lug."
However, many found Stallone convincing portraying a monosyllabic, punch-drunk Italian. They later realised he was simply being Sylvester Stallone.
I think critics made a similar error reviewing Portman's effort in Black Swan. Greater attention to the concluding scenes reveals that Portman's "performance" is smoke and mirrors -- kinetic editing and whip-pan camerawork suggesting emotional turmoil; and nothing of substance behind the trickery and attractive facade.
You can probably tell, I really didn't like Black Swan.