I would bet on the PS2.
Why?
Simple, the PS2 is platform that has backwards compatiblity so it already has a market waiting for it eventhough developers don't develop for it yet.
The PS2 also is released "now" and that makes a difference. Besides, when Sony actually manages to provide enough PS2's for the market, the "latent" buyers will flood the market and with such a vast market the PS2 will surely win the X-Box
I remember someone saying that the programmers are lazy, right? Although the PC platform has a wide range of games and fantastic graphics, a lot of people still stick to the pixelated PS platform. Why? Ease of use and no such thing as big bugs. When programming the X-box, the same problem and attitude will apply thus causing the X-box to be failure. You might say the only reason PC programmes have big bugs is because PC's have many different hardware configs. True, but when Microsoft is in charge they will surely bring in all their stupid stuff like "DirectX 9.0 for X-box!" updates and programmers have to update their software and knowledge while X-box users have to make update to their bios of firmware. If that is the case, will the programmers ever master anything???
Look at it this way....
Eventhough Microsoft is a giant in the PC software industry, Sony itself is a giant in the gaming and electronics industry. So lets say money goes into marketing, who do you think will win? The X-box is made of components that are done by multiple companies so not much of the profit goes to Microsoft. For Sony, most but not all of the components are done by Sony themselves so most of the revenue goes to Sony. This also makes them become less dependant on suppliers.
So, what's the final verdict?
The PS2 will be a sure winner but only time will tell the fate of the X-Box. The X-Box has a chance of winning over the PS2 only if Microsoft plays its cards properly. But looking at Microsoft's performance lately, it really looks unlikely.