Well, I disagree. There's been a 5 year gap between the release of the Ps2 and the Ps3. By 2003, or even 2002, the PS2 was already outdated, compared to the latest cards out at that time. Just you wait, this time next year the PCs will by far outdo the 360, perhaps even the PS3.
Also, you say that "It is kept in mind that the game works on atleast one generation older card, otherwise no one would buy it" . Yes, that is kept in mind. That's why ingame you can go to options and lower the graphical settings for it to run on your computer. Someone with a 7800GT, for example, would set it all to Ultra high, while someone with a 5200 or a 9600 would set it to medium, or even low. Take AoE3 for instance. At low settings it can run on even some of the older cards, while on ultra high the graphics are just breathtaking.