In this hypothetical question, if I had to choose one at launch, it's PS3 time. I'm pretty stoked about the PS3, even though in actuality I probably won't get one till next year. Yeah the high pricepoint blows, but if online is delivered Xbox Live style it is going to be the ultimate system. It'll have the best from the east and the west, full BC with PS2 (which is important to me. More important than PS1 BC on PS2), with a great online service, sign me up.
I've been watching Sony closely ever since they said they wanted to continue to support the PS2 well, even in the face of the PS3 launch. And at the moment I am really impressed that they are actually delivering on that promise. So if I do end up spending 500 to 600 dollars on a Playstation 3, I actually believe that the purchase will last me around 8 to 10 years.