The Wii is on track this year to beat the Playstation 2s best and record holding year. While its not set in concrete yet it is believed that the console will surpass the total of PS2s sold in 2003. And while the Wii might beat out the PS2 this year its not that far away from its total sales either. The Wii is currently sitting on 35 million sold and the PS2 on 43 million since its launch.
Source: Forbes