eptica, it sounds like you are asking if you can use the iMac G5 as a screen to play your PS2 games system through. I am afraid to say that the screen will only operate with the computer - i.e. you cannot have any external visual input into the iMac G5.
In short, no.
P.S. You can physically connect them, but nothing happens.
In short, no.
P.S. You can physically connect them, but nothing happens.