The PS2 is probably going to remain ahead of the Wii in terms of LTD sales as the thing just keeps selling. However if we discuss them as phenomenoms in the market, Nintendo has arguable achieved more against far heavier opposition and they have done so almost solely on the backs of their first party software efforts which may remain unparrelled as far as first party exclusive system sellers are concerned.
Oh and the DS is sure to pass the PS2, that much you can count on.