With a real good video card you can certanly emulate a Ps2 a quadro form nvidia for a station can surpase the power of a ps2.
But this kinda of video card is very very very very expensive, the most afordable and with the better power, and a "decent price" is the quadroo dcc.
But this it is not as powerfull as the ps2 in some aspects, anyway this is the kinda of video card that is required for using Maya (The best 3d prog).
still there is more power full video cards on teh market but as i said they are to expensive.
After all, the games for this platafforms are made on a cpu.
For example see the game from lucas arts star wars galaxsis i has the greatest graphics i ever seen or The elder scrolls III Morrowind.
I think that i pc can beat a Ps2.
This games will be in market in this year a some others too.
This are the kinda of games that will really make some competicion with teh Ps2 games
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never underestimate the stupidity of the human race