Guild Wars 2 accounted for 45% of the company's sales in Q4, followed by Lineage (24%) and Blade & Soul (10%). ArenaNet's newest game increased the North American market from 16% in Q3 to 25% in Q4.
It's not completely sunshine and roses, however. Lineage II and Aion both experienced declines during the period. NCsoft's net income was in the red for the quarter and its stock has slid since September, losing half of its value in the process.
[Thanks to Paul for the tip!]