Continuity mistake: When Jude Law and Joseph Fiennes are walking through the Soviet Headquarters and talking about how the sniper never relocates, in the first scenes, Jude Law has no bandage on his wound on his head, however in the later close up shot there is a bandage, this within a few minutes. There definitely is no bandage present in the first scenes. (00:45:20)
Continuity mistake: During Danilov's escape sequence, there is a rollover of a vehicle. While the vehicle's wheels are still turning, the tyre tread is of a modern all-season radial. When you see the vehicle again, it is a tyre more fitting for the time period. (00:14:55)
Factual error: When Commisar Danilov is dictating a letter to Vasily he spells out the word "honor" including the letter "h". There is no letter "h" or any equivalent in the Cyrillic alphabet or Russian language.
Visible crew/equipment: When the Russian army rushes through to the Germans, you can see a camera crew briefly on the right. (00:13:30)
Audio problem: When Danilov is reading the article to Vassili, we see it from a long shot. However, his lips didn't move. (00:20:40)
Continuity mistake: When the boats come under attack from the Germans, we see a senior officer with a red band round his hat get shot and fall back into all the troops. A few seconds later, the same man is seen firing at the planes. Camera does another double cut, and gets shot again. This is not a filming technique to show the same shot from different angles as we see him shooting back after being killed the first time. (00:08:30)
Revealing mistake: When the car flips at the start, you can see that a ramp has been made especially for the stunt. (00:14:50)
Audio problem: We see a Russian commander giving the order that one person gets a gun and a second follows him - the audio is out of sync. It is not another person giving the orders that we can hear, as we prominently see him shout with a megaphone. (00:09:45)
Revealing mistake: At the start when the Russians are on the boat and being shot at via the planes, if you look really carefully you can see blood packs visible just as they get shot. (00:08:15)
Factual error: Sometime in the movie somebody (I think the boy) says the Nagant rifle that Jude Law uses has a 4 times magnifying scope. When you compare the distance that objects have in the movie without scoping and through the scope of the rifle the magnification is way bigger than just four times. I know that cause I own a 4x scope myself.
Continuity mistake: As Koulikov is shot while jumping the gap we see the blood spatter created lies along the dark line above the red writing. In the next shot it shows the spatter from another angle in which we see that it is now above the dark line where it was originally. (00:58:30)
Visible crew/equipment: After it has been discovered Sacha is dead, Tania is arguing with Vassilli. He is trying to prevent her from running to him. The camera gets close to the action and the shadow of its operator is blatantly visible on the actors.
Continuity mistake: When we first see the girl, her hair is swept to the viewers' left. In the next shot, just 2 seconds later, some is over her eye and there is a gap where the hair was. (00:03:30)
Continuity mistake: At the start, when we see a close up of Vassili's gun, you can see a big clear knot just by the barrel end, a few shots later the knot is a lot smaller and harder to see. (00:02:30)
Continuity mistake: When we first see the wolf at the start it has got snow all over its fur. A few shots later the snow has vanished completely. (00:01:40)
Continuity mistake: When we first see the girl in the rail car her jacket is a dark green. In the close up it is grey. (00:03:30)
Answer: For the same reason Marlon Brando and Gene Hackman were top billed in Superman. He was a bigger name and his agent was able to negotiate a better deal.